With a short bow, you will encounter a couple of thigns that might limit your performance.
One is string angle at the tips, when you approach 90 degrees there you start to lose your lever effect and the bow begins stacking. YOu can get around this with a slight flip of the tips, this uses more length though and reduces working limb length. So you want to keep those as short as possible.
Second, is limited amount of working limb. This means you are really stressing your bow wood for a given poundage. Nothing wrong with that but it means tiller has to be more nearly perfect since it will be easy to overstress an area. One way around this, is to make a bendy handle bow. that way you aren't wasting valuable length on a nonworking handle. Another way to go is to make the bow limbs as wide as you can, this gives more wood but there comes a point where you can get too wide for an easy tiller. Wide means thin, and thin means a very touchy thickness taper.
I've generally had success with the rule of thumb of "working limb length nearly equal to draw length". That means 27x2=54" for my 27" draw. You can cheat that as much as you want, of course. The probability of success (Paul Comstock's phrase) just goes down incrementally. I'd also incorporate flipped tips and select an appropriate width to go with my wood choice.
As for 55lb being powerful, that is generally considered enough to hunt whitetails and anything smaller. I think the consensus is 60 and up for elk, both because of the animal's size and the fact that the typical shot is from a longer distance.
