Hi, I can supply you one of these:
Indespension Super Roller Coaster 10
Personally I don't think you need the 'EX'. The SRC10 has a hull capacity of 7.3m and you can lose at least a metre from a RIB length, when looking at trailer specs, due to the tube overhang.
Can do one of these, delivered to you (Cambridge?) before the end of the week, for £3750 all in. (Saving of £445.00 over RRP).
If you want to chat about it feel free to drop me a line on 07921 853190.
All the best, Ben