I realize this post was quite a while ago but, I've been thinking of trying something similar. Do you have any findings to report from your rain lab?
I suppose the main one is that I need to spend some time calibrating the tipping bucket gauges before I compare them any more. To that end, I've accumulated the equipment to build an automated calibrator (peristaltic chemical feed pump, calibration column, industrial controller, etc), and formulated a program to do the calibration runs.
I got a little wrapped up in using 2 of the Hydreon RG11s to estimate raindrop size, and also in elder care.
Lately, I've been measuring micro-local variations in rainfall with a Stratus gauge and 2 4" PVC Stratus clones, all within a foot or so of each other.