EKM, are the cross bolts that you are talking about the same as in the picture doublea posted? Could you post a pic? I'm not sure I understand the whole theory behind them. Is it only to strengthen the stock?
Exactly like AA's picture (only mine has one thru the wrist plus the internals, overkill perhaps, but strong as a bank vault). For a pic, go to accuratereloading_com, big bore section, and search "ELKampMaster, CZ, Stock" the pictures used to all be there along with the "how we did it."
Yes, a split stock is essentially the result of (1) the sides bulging out due to the recoil, usually at the weakest point, i.e. the magazine well (think about it); and/or (2) the tang which if the wood is not relieved,starts to resemble a wood spliting maul with the cartridge energy providing the "hammer." With that much recoil, things move.... not much.... but they move,it don't take much to have trouble if you don't have containment.
Accuratereloading_com has it's share of bigbore newbies (and pros) who tried to take the short cut ignoring advice to beef them up if they haven't been worked on at the factory and ended up with a split.... this ain't your daddy's 270.
A 416 Rigby owner thatcan't standa little frisky recoil?
Muzzlebrake should help, should still have a properly built rifle though.