I really wouldn't say going to COP's is "exotic", loads of people here have done it, and with the mentioned adapter harnesses is easier, cheaper, and faster to replace than swapping wires. I got four sticks off ebay with a harness for $40, hour later had them wired in and installed. Easier starting, crisper throttle response, no more plug wires/boots to corrode or replace. Never so much as a hiccup even in torrential rain.
To me it's kind of a no-brainer. For the same price, or less, of a new set of wires, you can get COPs that will last virtually forever, and perform better. COPs have replaced wires in new machines almost universally for a reason.
Anyway, why do you want an 8mm? It'll just be kind of a hassle to shove in the coil, and gives zero benefits over the proper 7mm size.
Don't buy into any claims that wires will "upgrade" your performance. The best they can do is restore performance lost by the old wires, in which case any new wire would seem to be an "upgrade". The claims about fatter wires, spiral conductors, and "capacitor" wires have been debunked time after time as, at best, equivalent to OEM, and usually, worse.