Im doing this currently....same style chonda 6.5hp copy.
I hadnt seen this thread but came across the same issues.
My solution was to make some "droppers" from 50mm x 6mm flat steel and a new axle from 16mm round bar. A 20mm axle spacer is also required. Mine is a stack of m16 washers at the moment.
The droppers bolt onto the outside of the existing frame through the handle bolt holes. I removed the original axle and used it's hole as a third bolting point.
It could of course be welded.
This drops the wheels down by 20mm and also spreads the left one by an additional 20mm. A quick test run shows no induced balance or handling issues.
No pictures yet I'm afraid as it is still a prototype mess.
An additional issue I have is that the internal drive shaft and coupling end is worn. It seems to run wobbly and clatters off the inside of the tubing/boom.
I believe this, in combination with some cracks in the main mounting plate allowing the boom to move is what killed the previous engine.
I have welded the boom back in place but there is still noise so that is my current point of investigation.
