Keep in mind when worrying about baggage limits that the fee on the Cayman Express flights to and from LC and between LC and CB is only $0.50 per pound that you are over the limit. So even being 20# over is only a $10 extra cost. I pack more for whatever limits I have on the flights to and from the US and don't worry much about the fees on the twin otter flights.
That's good to know, the photographer guy that I overheard being charged for overweight at LCM was paying a lot more than that. I am not sure but I seem to recall that it was around $80 or $90, so he must have had a lot of gear! And I suppose the conversion factor between CID and USD was also a factor.