Up until recently, I have used tuneomatics on my builds. A simple mod by removing the first and last saddles to accommodate a 4 string guitar.  I just screw the bridge down without thumbwheels or  the wooden base. Fits a flat top nicely without any mods to the wood or box as you would a telecaster.

Anyway, I thought there should be a 4 saddle tune-o-matic floating around so I spent a whole night googling for one.  I saw some bass versions but the measurements proved to be too large for a CBG.  Then I came across a forum for mandolins, Mandolin Cafe I think. And they were discussing electric mandolins and tune-o-matics and saw this.  They are not for sale though and the luthier who made them is not interested anymore due to medical and family reasons.

I was wondering if perhaps one day, if CB Gitty will make the perfect tune o matics for CBGs. The market is open right now and no one else is making them. Could be an opportunity for you.