From what I can tell, that's it.

I've posted the first photo of Magic Lantern using the DP1 HDMI display. The firmware needs to be booted with the cable plugged in and the bitmap display doesn't line up anymore, but the first step is mostly working.

EDIT: The log file shows the switch to 480 mode, although the frame buffer doesn't seem to change size. This gives me hope.
[pre]
4125: 17140.743 [BmpDDev] ChangePhysicalScreen (PUB) 0x43F80008
4126: 17146.936 [BIND] bindReceiveNewTFTOLC
4127: 17146.995 [GUI_E] GUI_Control:59 0x88f05c
4128: 17147.088 [MAGIC] Event: 0, 3b, 88f05c, 7
4129: 17151.243 [GUI] HDMI_VIDEO_CODE 5
4130: 17151.347 [DISP] SetDisplayType (PUB) 5->3, fDisplayTurnOn=1
4131: 17151.401 [DISP] WARN PB Reset(2783)
4132: 17151.602 [HDMI] ConnectHDMI : Already Connected
4133: 17151.718 [HDMI] Pana_TurnOnHDMI (Audio = 1)
4134: 17151.767 [HDMI] hdmiWaitForStat (stat = 1)
4135: 17153.689 [HDMI] hdmiWaitForStat : OK (3)
4136: 17153.886 [DISP] SetPBForHDMI DispType=3 fChange=1 HDMIInit=0
4137: 17154.190 [HDMI] ### 0x17d31d, EOS 5D Mark II
4138: 17154.243 [HDMI] Pana_TurnOnHDMI : EDID_COLOR_444
4139: 17154.271 [HDMI] Pana_TurnOnHDMI : FULL_HD_60
4140: 17154.393 [HDMI] hdmiWaitForAvreq (V = 1, 3, A = 1, 1)
4148: 17239.091 [IMP] [FEN] _ProcessFencingC 1510
4156: 17357.661 [HDMI] hdmiWaitForAvreq : OK (V = 0, A = 0, sink = 2)
4157: 17357.686 [HDMI] Pana_TurnOnHDMI : End
[/pre]

5D to DP1
 

Nice looking image. So does this ...

"EDIT: The log file shows the switch to 480 mode, although the frame buffer doesn't seem to change size. This gives me hope."

...mean that you are hopeful that the switch to 480 mode can be avoided and the output
maintain at 1080?
That would be cool. Sure motivates me to want to find an answer to my Glidecam-Wire snaking dilemma!

That is what I'm working on this afternoon. I've added code to call the descriptively named ChangeHDMIOutputSizeToFULLHD() function while recording video. The DP1 flashes as if it has switched to a new mode, but then immediately flickers again and syncs up with 480p.

Looking in the log file, it appears that the movie recording code is continuously checking for a non-480p video setting and calling ChangeHDMIOutputsizeToVGA() to remedy it.

Log file section where my code tries to fix the resolution:
8590: 29142.589 [MAGIC] Attempting to set full HD
8591: 29142.634 [GUI] ChangeHDMIOutputSizeToFULLHD GUI_GetDisplayType(5)
8592: 29142.864 [HDMI] [EDID] dwVideoCode = 5
8593: 29142.929 [HDMI] [EDID] dwHsize = 1920
8594: 29142.960 [HDMI] [EDID] dwVsize = 1080
8595: 29142.985 [HDMI] [EDID] ScaningMode = EDID_INTERLACE(i)
8596: 29143.005 [HDMI] [EDID] VerticalFreq = EDID_FREQ_60Hz
8597: 29143.023 [HDMI] [EDID] AspectRatio = EDID_ASPECT_16x9
8598: 29143.042 [HDMI] [EDID] AudioMode = EDID_AUDIO_LINEAR_PCM
8599: 29143.061 [HDMI] [EDID] ColorMode = EDID_COLOR_444

And a few frames later:
8725: 29520.692 [DISP] SetDisplayType finish Type=3
8726: 29520.766 [GUI] ChangeHDMIOutputSizeToVGA GUI_GetDisplayType(3)
8727: 29520.908 [HDMI] [EDID] dwVideoCode = 2
8728: 29520.946 [HDMI] [EDID] dwHsize = 720
8729: 29520.975 [HDMI] [EDID] dwVsize = 480
8730: 29521.002 [HDMI] [EDID] ScaningMode = EDID_NON_INTERLACE(p)
8731: 29521.025 [HDMI] [EDID] VerticalFreq = EDID_FREQ_60Hz
8732: 29521.047 [HDMI] [EDID] AspectRatio = EDID_ASPECT_4x3
8733: 29521.067 [HDMI] [EDID] AudioMode = EDID_AUDIO_LINEAR_PCM
8734: 29521.087 [HDMI] [EDID] ColorMode = EDID_COLOR_444

As a layman, I wonder if this is indicative of hardware limitations or is just Canons way
of limiting the functions for more political reasons (read... less competition with other products)?

Is a mini-HDMI plug small enough? If that is OK then use a cable with mini-HDMI both ends pull it through the holes & then use an adaptor plug to make it full size HDMI again For only $2.97 each when QTY 50+ purchased - HDMI (Type A) Male to Mini-HDMI (Type C) Female Adapter | Mini-HDMI (Type C) <--> HDMI (Type A)

Nigel that is a great idea. I did think of that and got the statistics on the size of the mini HDMI. The width (the crucial factor for me) is .5 inch. This means the hole should be .6 inch. The diameter of the sled tube (see link several emails above) is only 1 inch.
Im afraid that drilling 2 - .6 inch holes (top and bottom of the tube) would compromise the
weight bearing ability of the object. My backup plan at this point is just to use the AV out sent to the smallHD DP1 monitor. This rig thrives on balance and the cord must run down thru the sled tube for all things to work. I do appreciate your creativity though.

I suspect that you could shave down the plastic part of the plug to get the desired size. The actual 'works' is just the metal part.

Boy, brilliant minds do think alike. I found an old HDMI cable and shaved the sides down to the metal as a test. It could make a difference. The only possible gotcha is I think the plastic might act as an RF shield....but as soon as I get the DP1 I will try out several scenarios before I start drilling.

The soon-to-be-released beta version of 0.1.5 supports HDMI output now, although the bitmap overlay still doesn't line up quite right and the zebras are all screwy. One advantage to using the HDMI output is that the headphone adapter on the A/V jack can be left plugged in all the time since Canon will use the HDMI if both are connected. I haven't verified if we are also getting audio on the HDMI cable since the DP1 is video only.

Additionally, I'm hoping that the staggered startup sequence will also fix the problems for folks with cards that didn't load 0.1.4 very well.

Tramm, you Rock
I hope you are starting to feel the $upport from people all over the world hanging on your laborious endeavors
J

OK... sounds like some great stuff happening in the near future.