I think Break Tackle will be a good choice. It gives you the option of risking a 2+ or 3+ dodge into a cage to sack the ball carrier.
Normally I'd develop GRs to do that (dauntless, strip ball etc - a 4+ dodge with RR is reasonably reliable) but getting the RO to do it is acceptable.
The other alternative is to give him tackle to give the maximum chance of flattening blodgers - and also complimenting his tail quite nicely.
Finally, if you use him as LOS fodder (rather than a blitzer) Guard is a good choice. Guard is never a bad choice anyway
