I've spent a good deal of this last season trying out various configurations of sliding float in river depths of 15+ feet deep with very substantial success.
No time to go into all the details but basically I recommmend using a waggler with just the bottom eye as it slides a lot easier - lies flat on the surface til the stop knot hits - unless you are fishing stick float style with a shoulder ring.
Use the thinnest / smallest ring you can on the float, this enables you to use thin mono to tie your stop knot (with at least one inch tags). That in turn cures most of the problems with rod rings Keith refers to - tiny knot, just shoots through.
I was doubtful about using very small rings on the float but the diameter of the ring seems to make little or no difference to how well the mainline slides through and I have ended up using the shank and ring of eyed size 18's and even 20's with no real problem (just snip off bend and hook point with pliers, drop of araldite on the shaft and stick it into the bottom of the float.... works a treat).
If using a top and bottom ring stick float style then I make the bottom one fairly large, the top side ring my small one. That said I didn't find slider style really works as stick float fishing, as when you try to hold back or guide the float the float just rides down the line away from the stop knot / pulls up.
Shotting.... large chunk of load in one big bulk on main line, 18 inch fine mono hook length with a few small tell tale size 8's or 10's. That way the float rides on top of the shot when casting and out of tangling position with the hook length, plus for deep swims it depth charges the bait down quick. If it doesn't cock then you have a bite on the drop....
Good luck and enjoy; I found it massively more productive than legering and bite indication not compromised at all by the length of line below it. Mind you, I do use braid mainline, so no stretch nonsense plus very thin diameter helps the sliding through bit.