Nice Elite. You may end up putting that box back on soon as it is a great storage place. Also the mirror is helpful. 55mph sounds about right for the Elite 150. I weigh a little less than you do and mine does about 63(on the screen, GPS is about 59). That is with the carb way over jetted and a uni filter stuck right on the carb. You don't want to mess with it too much, they last damn near forever in stock form. Also, do much with the jets and air flow and loose the fuel milage. I get about 40mpg, not good at all. Check out the rollers and replace if needed, also might be a good time for a new belt. Don't buy a chinese carb for it off ebay, they are crap. Ive got one that i really had no other choice since i couldn't find the stock one(my fault for removing and letting it sit for a few years). Ive got 2 stockers off junk bikes now that im going to rework and use. Im going back to stock jetting and air filter.
Please for the sake of a very pretty scooter, don't mess it up. Its hard to find them that nice anymore. The red colour is nice. To me they don't look right without that box since mine has always had one on it.