I used to have my L7 vampire with the L91 triactis in a 29 g (and 4 L204 flash). When I upgraded to a 56 g column, I moved the L7 to the 75g with the 2 (now 3) L114 pseudacanthicus. The L91 and L7 got along ok, but it was clear that the L91 was the king of the tank. I moved the L7 as the L91 (dragon fin) is more valuable, and I was worried there could be future problems as the L7 got bigger.
The L7, now in the 75g with the L114s are doing fine; interestingly they all congegrate in the back right corner of the tank, probably as there is higher current from the cannister filter intake. I'll have to watch out as they get bigger that there are no fights with severe injuries.
So yes, I think they may be ok. Have plenty of hiding places, and watch out for aggression.
Also, these guys surprisingly like veggies (like zuchinni); you may want to feed them veggies occassionally to prevent bloat. Also, they (or at least my sultan before it died, and the L91 and L7) like the stems of amazon swords.