shell 2 deep safeties out of 3-5

i've seen it done that way...we bump our corner back and walk our dog (spur) out on #1 and play it that way, simply because we feel our corner is a better deep 1/2 player than our spur...we do bump our linebackers to put us in that 3-4 look, and we also at times put one of our stack backers down as an end and that gives us a 4-3 look...but in my opinion, you have to do something to give yourself some help on the edge to the side that you are rotating coverage...

We assign our weak side corner as the 1/2 player, and our spur would walk out on number 1 and the olb would adjust to two......

We are not a 3-3/3-5 stack team, we are a 4-2/4-4 but the same question/principles apply to us. We have done it both ways. This season we put the boundary side CB back and last season we dropped the OLB back as the "2nd safety". Some of these points have already been mentioned but this is what we have found:

Dropping the OLB
1. Gives you more flexibility if you want to adjust quickly and easily to that look vs. motions or vs. formations that you don't necessarily expect.
2. Allows you to keep your CB on the #1WR, which may be better for some situations (for example 2-deep/man-under coverage).
3. A little easier to move in and out of the 8-man front look quickly.

Rolling the CB back
1. Theoretically gives you a better deep defender or at least you never have to rep your OLB in deep technique.
2. If you go to a quarter/quarter/half type of plan the zone coverage responsibilities remain consistent with 3-deep (though you should rep the "bumped" OLB on reading #2 and sinking to more depth with no flat threat). All of the other "2-deep" coverage varaiations are still available.
3. Related to #2, the OLB can still be considered a force defender, albeit from a further-removed position.

To sum it up: either works but it all depends on the kind of players you have at each postion and what they are capable of and also the amount of different things you want to do out of it. I'd say we prefer rolling the CB back. It seems to allow for fewer changes to our scheme for the LB's who are already much more burdened with learning than everyone else. One note, however, we did often make a sub for that bumped OLB, though it was not mandatory.