I just used a Baggs piezo bridge saddle on a chambered body 4-string bass. you really gotta know how to fit a bridge saddle if you plan to use one of these - or take it to an authorized shop to have it installed
I have a strat hardtail x-bridge I bought from ildar... I haven't installed it but I spoke to L.R.Baggs support on the phone and they were very helpful in explaining how to do it. It's only got two wires so it should not be difficult to install.