Remember that the existing 82mm stroke is pushing it already, The factory had to notch the A15 oil pan to clear the rods & you want to add another quarter inch to the stroke.

If you have an A15, then I suggest that you mount it in your stand, invert it, pull the pan & turn the crank while watching very closely at how much clearance you have in there. It's not much at times.
I believe that the end of the oil pump shaft comes pretty close to something.

I suspect that to gain another 1/4" on the stroke you would need to weld & grind, but by offset grinding alone & using 1mm oversize bearings [on a 1mm undersize journal] you will gain 1mm increase in the stroke, but that would be the limit using this method.