I'd love to see someone have a go, however it's not something I'm interested in personally. I think the 1040-70 is the best base for one of these engines from a power-reliability and $-power stand point.
Stroking is pretty easy to do in small amounts, just grind the big end bearing journal to a smaller diameter essentially moving it's centre point further to the outside, and increasing the stroke as a result. Downside is you weaken the crank, and need to find rods with a smaller big end to suit.
I guess you could easily have the bearings built up and re-ground to the outside, you would need to have the crank de-stressed or normalised some how, but it could be done
Rod to case clearance may be an issue?
Keep us posted with your findings!