Hey man,
I have a Mex strat (but with a rosewood fingerboard) and there is no room under the scratch plate for change. Have a look next time you change the strings. If you want hot pups go for the Apaches or Irish Tours. Apaches are beautiful in in position 4, thats pretty much all i use. The irish tours sound sweet too, and distorted they are amazing. You can easily fool someone into thinking they are hearing humbuckers when distorted, tis ace.
On my Irish Tour strat (USA, Maple FBoard) i have a 4-way swich with just the brdige and mid pups, they are NOT RW/RP so there is no drop when i use them in parallel (which is how pups run in pos 2 and 4). This is a cool idea, i love it.
What sort of single coil sound do you want, and what is more important, you clean or distorted sound?? which is easier to manipulate to sound different?
Joe