Colin isnt CTP anymore
It's now Don Maclaine, but I suggest you don't contact him direct but go via the Flight Ops dept or through customer support at Yeovil if you want to talk to WHL direct. However the good advice you have got here is probably correct in that the squadron is more likely to be able to answer specific operational questions than the design authority.
RAF Merlins are now cleared to operate at 15600 kg (albiet with twin wheels on the main gear) rather than 14600 kg like the CSHs so that may be something to take into account, although if you are going that big why not scale for a CH47 to cover all UK aircraft types?
Dont assume that the aircraft is NVG compatible, RN aircraft aren't but I guess that covers other platforms as well
DM