There are 2 "flavors" of single bolt twist on mast base plates.
The good ones are "on center" (the bolt that engages the nut down in the mast box
is directly on center with the tendon or rubber uni joint.
The ones that tend to "unscrew" are the ones with the clamping stud off center from the tendon or uni joint.
Lots of people like the 2 bolt models, but they tend to restrict the amount of fore and aft adjustment in your mast slot by around 4".
This can put your mast base in a not so good place on many of the newer boards with very short mast slots.
The 2 bolt bases are most often used by wave sailors.
Slalom racers, formula racers (with huge 10-12.5 m2 rigs) and most back and forth sailors use on center, single bolt, bases to avoid the mast slot length/postioning issue.
The single bolt bases are plenty strong enough unless you are wavesailing where the board and rig are likely to get "rolled" by the surf.
Hope this helps,