:behindsofa:
NO !!.....
The seat in the cylinder is machined to accept a single flare and the seal would be compromised if a double flare is used.
With your thinking, you would only need to double flare everything irregardless of the seat type.
I am getting concerned now with your approach to this job and I personally think that you are likely to make what could be a potentially fatal error
Brakes and tyres are the only thing between you and the graveyard and if just carrying on without knowing exactly what you are doing, you should leave the job to someone who does know.
This is nothing personal against you, but I can see a disaster waiting to happen here and that's the best advice I can give you.
Please heed what I say, but no doubt others will comment on this topic who are in a similar frame of mind as myself.