I agree with Slyfox; those inserts are mandatory. Without them the compression ring just collapses the plastic tube without getting a good seal.....
it will be like turning the faucet down and getting a little trickle of water. so no brakes is the result. have to put those insert in to keep things open and flowing.
steve
slyfox
model IV 1200-flying
912uls
IVO medium in-flight
RV7A-flying
IO-360
constant speed prop