RE: servo reversing y-harness
As said above by someone there is a pot for fine tuning the throws on a reversing Y....that is where the problem lies....a printed circuit board in the middle of a wire....or just a wire......
You'll find some folks that will tell you they have never had a problem with a fuel valve...although I think the majority on here will tell you not to use one as it will leak someday....
But it's your airplane....
Good luck