You missed it Rob --- it's in the first post.
-----------bore-stroke-cc----TP--------TP volume---scr--------piston weight
HW99s ---26----71---37.7--3x17?------0.120-----314:1------235 - 225 - 225g piston with seal and no
liner. Add 10g if you leave the weight inside
the piston
I'm pretty sure that the transfer port would be nearer to 16mm in length --- My findings are a couple of posts up.
All the best Mick