Been using SMPs for almost 4 years. Since May/2008. Better than 25,000 commuter/utility miles now w/2 flats and 1 slow leak. Replaced the rear tire @ 10,000 miles. My main 'loaded' commuter is a CX bike. 700x28mm w/Forte extra thick tubes. My other commuter is a 80s Fuji Del-Rey converted to fg. I run SMPs on it as well. 700x25mm also w/Fortes. Around 6,500 miles in the same time span. No flats or leaks. Just replaced the rear tire. The combo is heavy, but when the object is to 'get there' I'll take the extra effort for the peace of mind in knowing I've got, arguably the best flat protection on the market. Even still I always leave my self an extra ten minutes, timewise...just in case. Usually, the bike is so weighted a few etra grams or rolling resistance doesn't make that much difference, anyway.

Btw, the SMPs are a ***** to mount, so a Kool Stop tire lever is a good tool to have around. They're only around 10-15.00USD...worth it! And the Fortes don't accept a patch very well, so it's a good idea to carry a standard tube or two one size smaller than your tires call for in emergencies. Along w/a patch kit,of course.

Given your size I'd stick w/35mm or maybe jump up to 40s. Whether you go w/t MPs or the Supremes they both offer great flat protection w/t Supremes having a little less, but having better wet traction. And having done the 'Grand Tour' of Ireland a few years ago I know all about riding on wet roads.