I don't think a one piece mount is going to increase rigidity any.

On my .30-06 110 I personally upgraded to Weaver Grand Slam Bases and Warne vertical split rings (both steel). Weighs a few ounces more than the package stuff that came on the rifle but worth it IMHO.
On my long action I had trouble with the rings being too far apart to mount the scope so for the front base I ended up going with an extension base. It hangs over the action opening a tad to extend out but a nice solid steel base won't flex any there. On a short action I doubt it would even be an issue.

If you're concerned about weight I'd look into the Talley lightweights. Less points of failure there since you're effectively just screwing the rings onto the receiver.