The piston modifications are not really rocket science
For the small end side of the conrod ( the GTi is wider than a Honda).
I filed out the piston (to both sides) sorry no picture.
I cut some grooves ( both sides ) in the piston for some snapclips.
And cut the piston pen on the rigth length.
On top i cut about 1,6mm off in a lathe.
For if ( I did my calculations right ) a CR of 11.1-1
Using a MLS SGP headgasket.
( the one on the right )
I checked the pistonhead / valve clearance with some solder wire
Using solid lifters and some high lift Tech3 cams
I did cheked all the weights