we get loads of floters in this neck of the woods - i'd guess a quarter to a third of all the canvases we get over the counter are asked to be floated. Usually with everything painted white, as has been the local "gallery" style for at least ten years.
Half the time we will screw straght through the back of some painted mdf into the stretcher bars, the MDF already cut to whatever size needed, the back of the mdf is best sealed with pva, and then just frame that, or, and this might just be arguably the best tip you will get,
use velcro.
This velcro gag is a huge fave among some of our artist customers as they can very quickly and easily swap paintings about in frames for exhibitions etc, as do some galleries who screw the frames to the wall and change the exhibits.
of course this only works best for galleries exhibiting regular same-sized works from regular artists, but if you hate doing floaters, you can suggest the velcro option, and if your artist goes for it you wont be making so many for them
