This one has a single cross bolt behind trigger. Newer models have 2, fore and aft of magazine. If I add the second cross bolt where should it go?

I have one with a single crossbolt in 416 Rigby with the European hogsback stock. I am shooting loads with a calculated 6200 ft lbs of muzzle energy and it has not shown any signs of stress cracks or stock splitting. It is glass bedded with the tang relieved of any contact. I would be more concerned with proper fitting than the second crossbolt.

Check your tang relief and bedding contacts for correct fitting and you should not have any problems. I agree a second crossbolt is beneficial but the bedding and tang relief are a much more crucial factor in an effort to prevent stock splitting. I have roughly 300 rounds of 350 grainers at 2800 fps,100 300 grainers at 2900 fps, and 100 rounds of 400 grainers at 2450 fps without any sign of stock splitting or chips. I may be lucky and have an exceptional piece of wood but think the advice of others to bed the stock and relieve the tang from contact has kept me from any problems.

Thanks Sid, looking into it as described. Appreciate the help

You're lucky you got a cross-bolt mate!
My later model CZ550 .458 didn't have any!
Had to get them fits by a 'smith..