Centerfeed ?? in SA action question -- 7mm SAUM

I am planning to move from 270 WSM in a 12FVSS to 7mm SAUM

Shilen will throat the barrel to my specs, specifically I can supply a dummy round seated to the COL that I desire.

But I am having questions about feeding. The SAUM and WSM rims are very similar, so I do not anticipate problems there -- but I am worried about feeding a little.

Anyone have an idea about how much trouble I will have getting the 7mm SAUM to feed from the stock 270 WSM magazine?

Obviously, if I desire to use the magazine, I'll need to have the cartridge COL less that the magazine length. But how much shorter? I won't really be able to test feeding till I have the new barrel in place, but I'd like to get the throat reamed pretty close to correct, so that the there is little jump.

I plan to use the very ballistically optimized Berger VLD 180 gr hunting bullet.

My current plan is to seat a couple dummy rounds to a tad less that the SAMMI spec for 270 WSM and go with that. I assume that Savage designed the 270 WSM magazine for standard length cartridges and anything shorter than that ought to feed....

But the long Berger pill could benefit from being seated further out, to take less of the case capacity.

Anyone have thoughts or experience?