The ideal overall length of FLÔTit tube (including the float) is determined by the keg’s shape & size. It should be the distance from liquid post’s opening to the keg’s bottom + 75% of the keg’s diameter (see the tube's geometry in Fig. 1 above). This length would keep the silicone tube from dragging on and stirring up the trub/sedimen. It helps keep the screened section of the float parallel with and 1/2" above the yeast cake when the keg is near empty. And it also keeps the float from “wandering” and coerces it to land at the opposite side of the liquid post (or under the gas post of Corny keg). To get most of beer out when the keg is near empty, just tip the keg toward the gas post so the most of the remain beer is pooled where the float is (under the gas post).
USEFUL TIP: For typical kegs, just cut the silicone tube equal to the height of the keg + 2" (as a margin of error). Try it and cut back later if need be.
To install FLÔTit:
1. Be sure to sanitize all the parts and your hands.
2. Connect an appropriate length of the 7mm OD silicone tube to the short stainless steel dip tube and insert it through the liquid nipple until the dip tube's O-ring is resting on the nipple. Re-install the liquid post by fingers until it stops turning and then turn another 1/2 to 3/4 turn with a wrench. Over-tightening will squeeze the integrated silicone too much and block the flow!!!
3. Use sanitized tongs or tool to fish the silicone tube out of the keg to connect its end to the tail of the float. Try to keep the tail in the float as you connect it to the silicone tube.
I made a HOOKit tool with stainless steel 3/32" welding rod for this and you can do the same (see photo above).
4. Drop the the connected float back inside the keg.
5. Reinstall the liquid post tightly on the keg’s nipple.
About my funky HOOKit tool. It's really a cool tool, hand bended from stainless steel welding rods. You can hook the tube, slide it toward the free end and twist the tool counterclockwise to grip it and pull it out of the keg. I think it's ingenious, but please tell me how you like it.