Well on the flight plan U should only enter the INITIAL requested altitude. If U want more than one FL along your route, it is best to make a subsequent request direct to ATC.
I haven't flown CYYZ-KMCO but I have flown CYYZ-KMIA & CYYZ-MYNN a number of times. U can actually put whatever FL U want in the flight plan (usually the one with the best forecast winds) caus' U'll probably get something different from ATC. Take-off from CYYZ, climb out & after a while U will B cleared, often DCT to destination, or if U're slightly less lucky to an enroute VOR. An intermediate clearance will occur if some SUA (eg Canaveral) is active @ the time. Otherwise I've been cruising DCT KMIA @ anything between FL350 & FL430.
MF
[ 03 October 2001: Message edited by: Manflex55 ]