I have no good experience with float variables in other projects especialy when it comes to big numbers. I didn't check it, but I think there was a reason to choose unsigned long. This goes up to 4,294,967,295. In float this becomes to 4.2949672E9, so we loose the last 2 digits. That may impact acuraty if there are realy numbers larger then 1E7.
As I understand the code, if its faster it's also more precise because of time for interrupts and so on? (See change to 20MHz crystal)
But it may be an option
