Piezo string balance on a Precision A/E

[ric426]

I just picked up a 18 year old fretless MIJ Precision A/E with a mag pickup and under saddle piezo pickup. I've put in a DIY Cafe Walter piezo buffer that helps out the piezo low end tremendously, but it's still got a weak sounding G string. I know about insuring that the bottom edge of the saddle and bottom of the saddle slot are flat and true, that the saddle isn't tilted, etc. Here's part of the porblem. I pulled the saddle and someone had shimmed it with a couple of paper strips, which to me doesn't seem like the best material to use. Plus, over time the shim has compressed the plastic covering on the piezo pickup (almost looks like heat shrink tubing). Obviously, the shim isn't very effective any more since the piezo covering has just conformed to it.
I've don't mind making a new saddle and have a suitable piece of bone saddle material for it, but I'm wondering if there are some saddle construction tips or tricks that might help bring up the G string level. A friend has a similar A/E that has a split saddle, but he says his is kind of weak on the G string too. I was wondering if it'd make sense to have separate saddle pieces for each string or if that'd just cause other problems. I've seen acoustic guitar saddles that were cut from the bottom edge up to about halfway, between each string. Would that help or is that done for another reason? Any suggestions beyond try it and see what happens?
I've thought about trying a new piezo element, but it'd be hard to find a ready made one long and wide enough to fit the slot and saddle properly. Does anyone know of any sources besides the big names (Fishman, LR Baggs, D-TAR) where I might find piezo pickup materials to experiment with?