Anyone use Tire-Safeguard's Tire Pressure Monitoring System?

I'm thinking about installing Tire-Safeguards TPM system since I noticed that my tires were loosing air due to the valve stems leaking. Seeing that I have to take the tires in and have new valve stems installed I thought it would be a good time to install a TPM system. I'd want to use the internal valve mounted transmitter thereby getting metal valve stems in the deal.

Question to those of you who have had new valve stems installed. When talking to Tire-Safeguard they needed to know what the valve hole size is. Does anyone know if on the 15" wheel the Valve hole is the standard size or the larger 5/8 hole?

Here's the link: www.tiresafeguard.com

The tires that I have are Goodyear Marathon Radials, Manufactured in the 29th week of 04. (PDHH MLOR 2904).
Come this June, we will be heading up to Searsmont, Maine which will be our longest trip to date, so I'm starting to get things ready now.