The top tube length is as important as the seat tube length, in my opinion. I have a longer-than-average torso, so a traditional "square" frame pattern (54x54) requires that I get a 120mm stem (usually...it really depends one frame geometry).

Anyway, I'd give it a try. Raise the saddle (you might have to get an extra long seatpost) FIRST, then see what you'd need for a stem. Raising the saddle also puts you back some, so you may not need as long of a stem as you initially think.

If you can make it work, a 55cm frame will be lighter than a 58cm frame for sure! Lighter is almost always better.