Torsion bar upgrade and suspension questions

[wowzer911]

I'm upgarding my rear torsion bars from stock 23mm to Carrera 24.1mm. Do I still use my normal 37+ degree spring plate setup, or will this substantially increase my ride height? Am I going to have to "do the math" to figure the correct setting? It just seems that 1.1mm isn't that big of an increase.
Also, I have Boge front shocks, but have installed Bilstein rear shocks. Is mixing hydraulic fronts w/ gas rears really as bad of a practice practice on t-bar suspensions as it is with sprung suspensions? I'm hoping to upgrade the fronts eventually as my budget allows.

[David]

Here's a calculator: http://vintagebus.com/cgi-bin/spring.cgi

[wowzer911]

Thanks,
I remember reading that article, but forgot about the calculator.
This adds one more question. What's the difference between Euro and USA ride heights? Also any takers on the mixing shocks question?