We try to accomodate all sizes of RIBs and certainly would make you welcome. At least one day is spent exploring the rivers so no problems with a small RIB.
For the longer trips (60m roundtrip to Southwold for example) a lot of it depends on the weather - there are going to be conditions at times where 6-7m RIBS are fine but a 3.65 would struggle. The thing to do in this case is to jump onboard one of the larger RIBS (there is always room and folks willing to take on crew) and enjoy the day!
Costs for this cruise are purely launching (a tenner), overnight mooring for a couple of nights and your accomodation, food and drink. No fee's to enter although for insurance purposes you must be a member of BIBOA (British Inflatable Boat Owners Association).
Format is usually to meet around 9.30 each morning decide on destination depending on weather and tides and head off with the aim of getting somewhere for lunch. Afternoons we head back to Levington and usually arrange to all meet up in the evening for a meal and refreshments. (The eating and drinking bit is highly important!
Hope this helps, If you want to know more drop me an email or PM.