Removable sheds on skull

I'm setting a pair of moose sheds on a skull and want to make them removable. I was wondering if any of you have done this with sheds and if anyone has any tips. I've attached smalleresume sheds to skulls (deer) but never anything this caliber. I forsee a problem holding them into place and keeping them there while I drill holes because the way moose lay out and the sheer weight per horn. Any tips would be greatly appreciated. Also does anybody know where I can buy the square inserts for skull and horns. I haven't done much research for that yet but could save some time. Thank you. I'll post pictures once it's done.

I used 1/2- 3/4" square tubing and drilled a slightly larger hole and bondo'd them in worked pretty slick. This was on a head that was have taxidermied tho.