The different sizes are really an intersection of ensuring the minimum amount of clearance around the mic to provide optimum wind protection, and ensuring that you have maximum flexibility in terms of distance for mic placement. The smaller windscreens simply let you place those shorter microphones (which are typically not supercardiod) closer to your sound ...
So are you thinking of not buying the one Rycote recommend? If so, I think you should trust Rycote and go for one the right size. The S-series kits are quite specific because of the way they hold the mic.
Larger blimps are heavier which is reason enough to go with one the right size.
TLM 103 are really of too large a form factor to be useful inside a blimp. You need there to be reasonable space between the inside of the blimp and the capsule. You should be looking at pencil condensor form-factor such as a shotgun mic or hyper-cardioid for dialogue. The most effective result for stereo recording inside a blimp will be to use M/S recording ...
Not KM184s, but it's kinda the same setup I guess:
I did the same thing with CM3s in a Rycote windshield a few days ago and have to say, that the mics were pretty vulnerable to wind. I guess this comes from the small distance between the capsules and the windshield.
depending on the wind conditions I've had good luck with the DPA foam windscreens. sound very transparent, lower profile and cost than a baby ball gag, and can get clean audio up to about 10-15 mph winds.
not for extreme conditions obviously, but they can at least get you outside.