Sounds pricey but would be willing to investigate the possibility if I could find a spare engine so I wouldn't f.u.b.a.r. mine in case I screw up.

When checking the measurements for the 100mm piston there was not enough room for a larger cylinder liner without boring the engine cases larger and if trying to do that then the bolt holes for the cylinder would be cut into.  That is a pretty hard problem to overcome unless you have new engine cases machined from scratch with a wider hole for the larger liner and for wider spacing for the cyl bolts, and then you would need a new cylinder machined that also had the wider bolt holes...makes everything difficult.