Re: shortboard type question
High performance short boards are more difficult to ride for a few reasons. They are narrower and thinner so do not have much flotation which makes it more difficult to catch the wave. . If you watch an experienced surfer on a high performance shortboard they make it look effortlessly, because they take off where the wave is steeper, and get to their feet quickly and smoothly, and have developed their timing to be able to do this. Another reason they are harder to ride is they can be very unstable. Most of that is from the fact that they are narrower and thinner and do not have much foam with them. Again to an experienced shortboard surfer the thinner narrower boards are much more lively, responsive and quick into turns, and experienced surfers like that feel.
I think if you have been riding a 6'0" Dumpster diver you may be ready. Just keep at it, and don't get discouraged just because it is more difficult. Try to take off in the more critical part of the wave where you still can make the drop, steep enough to where the wave will let you in without having to paddle like a mad man. Also keep your nose down and do not be to far back on your board when catching waves, as this can cause your board to push water, and make it harder to get your board sliding down the face of the wave.
Good luck and let me know how you do!