Mixed footage (HD and HDV) in Vegas
 

I am new to HDV and try to edit footage from SD cameras and HDV in one timeline to produce SD NTSC 4:3. When I import it to NTSC DV (720x480) tmeline I use for HDV footage "Event Pan/Crop" and choose "4:3 Standard TV aspect ratio". It looks GOOD! when I am previewing it in Vegas but when I export to tape HDV footage looks bad (very bad) not sharp and in strobe like mode. What to do to edit HDV and SD in one timeline. How to crop HDV so I can use only some fragment of the frame??? O, and in camera downconverted files (Canon HV20 and Sony HC1) look terrible!!!
Please help.
Thanks in advance.