I guess that's the point, you tighten your's so it won't move unless you want it to, I opt to not move mine and forego the swivel option completely. Lots of fellas I shoot with have the swivel version and they too state they tighten it but about every one of them at some point also state the thing moved when it was not too desirable. I don't know if it's a crutch they fall back upon for their errors/miscalculation or if it happens as often as they profess but I know for sure that mine will never swivel and as such have one less point of failure. (It's just my nature, weigh the possible benefit against the increased likelyhood of failure. If there is little or no benefit I won't opt for the additional failure point.)
I use the Poly Beads, they're relatively light and not deteriorated by the elements. They also have a smooth movement during manipulation/adjustment of the sand sock.
There are a few folks that use styrofoam beads, much lighter but I don't know about their durability (water, chemicals, compression, etc). I'm going to to find a bag of them and make a sock for testing.
I don't have any difficulty getting level with the non-swivel bipod. The legs are adjustable for length and I don't shoot from improved surfaces (asphalt, cement, wood, etc) except on rare instances (and these are usually pre-leveled). In the field and on the range I find that I can easily move my shooting position a few inches and find a spot that offers a little dip or rise to level to the last little degree. I also "load" the bipod when I shoot (apply pressure to the buttstock forcing the rifle forward) and as such nearly always make little depressions in the ground with the bipod feet (to capture the feet and prevent forward movement) before shooting. These custom depressions allow me to level the bipod any last little bit. It's a nearly automatic thing for me, very little wasted time and little movement as I do it as I extent the legs to the proper length.
I shoot often to 1000 yards in competitions (F-Class TR) and also when at tactical competions or at UKD (UnKnown Distance) field fire training/practice. My big game hunting is not to these 1000 yard distances but more generally in the 500 to 650 yard range.
I use the B-Square bubble level. I clamp it to the Badger base so it is visible at the rear left of rifle. I doesn't extend beyond the parallax know and is not problem.
Midway has them but you may be able to get a better price somewhere else (I didn't check price).
B-Square Bubble Level @ Midway