Sure, Richard, you could switch to some Ergo shifters and an eight speed 
freewheel and derailleur, but along with the extra cog youd acquire a good 
dose more of wheel dish and therefore a weaker rear wheel.  My recommendation 
would be to stick with what you have, assuming it's working well, and spend 
the money, if you have to, on a second set of wheels, maybe some tubulars, or 
a complete overhaul.  If you so go for eight, I'd recommend you have your 
frame spread to accept a hub at 135mm and have the appropriate axle and 
additional axle spacers added to help reduce the dish of the rear wheel.  
Hvae fun...
   -Brian
* SPITFIRE v3.51 Wheel Werks - WWW: http://www.wheelwerks.org
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