possible to "upgrade" multicart r10 to r12
 

So awhile ago I bought a multicart

Multi-Cart | Products

I got the r10 to both save a little and figuring I could always add the bigger steering side wheels later if I wanted. Wrong. I found out the frame is built differently on the different models, and the big wheels cannot fit on the r10 in such as way as to make it feasible.

Just wondering if there's anyone who's had the same idea and had success, WITHOUT mad welding/metalworking skills (which I don't have) in upgrading the small r10 tires to big rubber ones. Some kind of simple, off the shelf solution.

Or am I simply screwed unless I get an r12?