I'm using the same LRGB filters as Dennis, these are the Custom Scientific set made for SBIG.
There are more filter spectra responses on the
Custom Scientific website.
I would also recommend reading Alan Holmes (PH. D, optical science) article on the SBIG/CS filters -
http://www.sbig.com/pdffiles/SBIGFilterSet.pdf
I use a starting ratio of 1.35:1.0:1.65 (R:G:B) to compensate for the green wavelength sensitivity.