I'm gonna go for it without an additional lug in the test stock.

The 7mm, 300, 338, and 416Rug exists in multiple models without an additional lug, so I'm deferring to that experience for those barrels, so the only odd man out was going to be the 458WM. With a hefty bed of Devcon Steel behind the recoil lug, dual cross bolts, and a relieved tang, I'm going to give it a shot for about 100-200rnds of 458wm with the pattern stock - Circ Walnut, weaker than the Turk Walnut I'll have for the permanent stock.

If it does break, I'll add a dovetailed lug to the barrel, and as you mentioned Uncle, I'll shape/step the lug and relieve the "anchor" within the stock such that it can't touch the other barrels. If it doesn't, then I'll take the 100-200rnds as confirmation that it'll survive.

Of course, the whole thing's kinda on hold right now, spending my limited free time in the deer stand instead of the workshop!