Fwiw i have 3 kegs fitted with red caskwidge floats.. keep in mind corny kegs are thinner with a smaller diameter than the casks these are designed for..
Imho best results are achieved by swapping out the long product out dip tube with a 2nd short gas in dip tube, some may suggest cutting or bending the long dip tube but i would suggest the fiver or so spent on a new gas in dip tube is worth the flexibility of being able to switch back.. 'as new' product out tubes are not cheap or readily available, as quite a hew folk hack of an inch or 2 in an attempt to not draw an initial dirty slug of sediment, but it leaves the sediment in the keg just under the draw tube so some gets sucked up with every pint ..
Then when fitting look for the natural curve of the silicone tube and fix it so that expands across the full width of the keg. if not it can push against the keg wall and hamper the float sinking with the beer.
When filling pull the float out the lid hole fill, and then put the float in. If left in the keg bottom the curl of the silicone tube pushing up against the keg wall can hamper the floats ability to lift, and you dont want to go fishing in your clean beer
with the float attached to a 2nd gas in dip tube the float will fall to about the level of the bottom dome, so when the float stops drawing you will have the bottom dome volume left containing the beers sediment. So its a 'swings and rounderbouts' situation the dome bottom volume loss with a float and a dirty 1/2 pint out with a long dip tube..
the floats should allow you to pour clear beer sooner than you could with a long dip tube as the beer will clear from the top down If your beer is ready to sup that early is a question that only your taste and brewing can answer..
while they do work and do allow pouring of clear beer earlier than a standard keg, im on the fence about them and dont think i will add floats to more kegs..
AND There may soon be a cheaper alternative. the New Zealand or Aussie? Fermentasaurous? product has a nice simple float which looks very adaptable to use with kegs.. its not yet in the UK, Ebay has some fermentor float kits, but they contain extra fermentor h/w which bumps up the cost, give it a few months however and the floats may will appear as individual items??? and then may represent a cheaper 100%SS alternative
http://kegking.com.au/brewery-equipment/fermenters/fermentasaurus-float-and-dip-tube.html