I heard of a little experiment with an inflatable mast float. A new sailor had bought a used H16 that had known problems with the mast (Every time the original owner raised his mast, a bucket or so of water pour out along with the ants that lived in the mast). The new owner tried to seal the mast but could not seem to get it to work and wanted some extra protection. So, he bought a CO2 float and then rigged some lines to pull the float to the mast tip and fire the the float.
One absolutely windless day on the lake the owner and 4-5 helpers drank lots of beer, paddled the boat out to deep water, turtled the boat, rigged the float, got into position and fired it off. They said it was amazing out fast the mast came up and then they realized the boat didn't move. The mast came out of the base under the load. Now they have a upside down cat with the mast floating tip up beside them. They said it took hours to get the boat back on the trailer.
The owner decided to seal the mast, the right way. Apparently there was a foam plug inside the mast that was missing
Conclusion, when you buy your mast float off ebay first test it on a windless day with lots of help and then under the conditions you will have to use it.