#2 working on alu legs (ankles and boosters)

I've got a pair of alu legs from a friend (zhongvador).

the legs :

I've worked on mounting others parts on them.
for the boosters, i've started to fix double face scotch on the back of the booster and put the booster correctly on the legs. that helps me to get the right position for the outer ankle. And after, the ankle bracelet give me the alignment for the ankle.

I've got JAG outer ankles so they're bolt from the back side. i keep this method to attach them on the legs and drill the legs

here is my method to attach the boosters. my legs have 4 holes for the boosters but they are nothing on the back of the booster. how to make the holes in the boosters, aligned with the holes in the legs.
I put large parts of scotch under a sheet of paper (the fixing side is up) where i've marked the holes in the legs. the sheet of paper must stay on the leg and them put the booster over the paper sheet in the good position.
then attach the sheet to the booster, use the scotch parts for this and drill taped holes in the booster.