Hey Simon,
The Big Wheel is generally for the shorter paddler at around 5`11" max, your preeeetty tall so finding a good size playboat will be tough. You said you were in a lil joe? There is a bigger model called the liquid logic hoss, although im 6` and my legs dont quite fit (i cant believe you fit in the lil joe!!
Ok, what i recommend as an alternative to the Big Wheel is either the liquid logic biscuit 65 (a sweet boat) or perhaps the wavesport super ez. Liquid logic no longer make the biscuit (they have a new playboat called the freeride) but you could probably pick one up from eBay
Hope this helps and happy paddling!
Hamish