Triathlon on single-speed

Thanks to everyone who posted on the Triathlon fixed thread. I now know that fixed gear set ups are not allowed by the BTA.

So, I thought I'd try my next triathlon cycling single-speed (Thames Turbo, 25 August, www.thamesturbo.co.uk).

I've gone for a 18T freewheel, which will give me a gearing of 48:18.

Questions: is it easy to fit the freewheel to my flip-flop hub and, if yes, how is it done?

sorry to be blunt, but you will get caned on the bike.. the bike leg is in effect a time trial, go with gears.. and save some energy for the run..