Has anyone ever swapped in LESS firm shocks?

[DreamSign]

Ok, let me throw another shrimp on the BarBi...

If I went with 205 45 17 instead of 205 40 17 the Overall diameter is + 3.7% from stock
If I went with 245 45 17 rear instead of 255 40 17 the Overall is + 2.5% over stock.

Given there would be a 1.2% mismatch in RPM per mile compared to the stock OAD, Would this cause a problem with the computer, or ABS?

For the 17" wheelset I want to swap onto the 5 speed car, The rears are currently new 255 40 17 Firestone Indy 500s I just bought on the drive down from Canada, and the front tires are older and need to be replaced anyways.

What if I kept the current (less than 1000 miles on them) 255 40 17 in the rear and added the .2" taller than stock 205 45 17 @ 24.3" OAD vs the 245 45 17 at 24.1" OAD?

Basically this way I'm adding +5 to the sidewall profile, while keeping about the same weight of the tires. This 'should' soften the ride over the bad roads a tiny bit, probably enough to move the needle a tiny bit?? What say you?