I’ve been having some success with a 4x12 Clowns deck, it wins lowball quite consistently, cheats less often, dominates the board with its control spells, and when forced to fight, it can still shoot pretty well, given enough stud bullets (which is not a problem now that 4R has so many cheap shud hucksters).
As for Straight Flush builds, I tried doing Sloane and Law Dogs 2x16 + SF, but I didn’t get quite the effect I was hoping for: you win lowball more often and you can still shoot well enough, but Straight Flush still comes only once in a blue moon. Well, more often than that really, but you might just as well be playing 2x16 + scattered values.
In any case, if you’re building something other than 3x16 (with 6-8 off-value cards), you better have some control elements, maneuvering, and tricks up your sleeve.