I have been comparing a +30 Heplex with a +40 JP. Perhaps surprisingly, the JP is slightly thinner in the skirt than the Heplex so not much scope for removing weight there unless I shorten the whole skirt.
The Gudgeon bosses are shorter, but much thicker than the Heplex as much as 5mm thicker I would say. So I did think about milling 2mm each off the opposing faces, and possibly running an endmill along the four sides to remove say 1.5mm on each pass, that would still leave the bosses 3mm thicker than the Heplex.
The piston deck/ top/ crown is about 2mm thicker in the JP and the reinforcing rib is also much thicker than in the Heplex, but I dont think I have a milling cutter that would reach that deep.
I could take it off the top of the piston crown, but the top ring in the JP is about 2-3mm closer to the top than in the Heplex and I am worried about weakening the top land. I suppose I could leave a band full height around the piston perimeter just take the center down a bit, at the cost of losing a bit of CR. ( its a VB, would I even notice??)
Can anyone say why I shouldnt do any of this, or suggest another approach before I do something horribly expensive.