I am running a McRee on my 338RUM, R7L-TMAG to be exact. The AI magazines have to be "modified" to run the RUM family as the shoulder is farther forward than the 338 Lapua. The Modular stocks are going to be the most ridgid platform you can get. However the trade off is the increased weight, my 338RUM is over 16lbs IIRC. You don't want to be dragging that all over gods country, but then again, that's why you launch a 300grn bullet at almost 2800fps.
I REALLY like the looks of the KRG Whiskey 3 chassis but i'm afraid to ask if they offer a LH version
At first, I was like "WTH do you need a folding stock for?" Then, after learning I have to remove the cheek pieces to clean the rifle I understood
Not to mention being more compact during transporation, especially when you get into the uber long bbls usually associated with the new ELR rigs.
They are very ridgid, usually very heavy (mine is)... the McRees offers the same grip as the AR-15/M-16 platform that everyone is familiar with. Function & reliability has been 100% as of now & hey, if you run out of bullets you can use it as a club!
Hope that helps,