I dont wanna say its safe to drive. Any gap you have between a mc and a booster is never good since you never get the full force of braking and also it probably doesn't allow the pistons to return fully. It could be a bad booster since the rod isnt adjustable. However also keep in mind a bad mc can deff lock up the brakes as well. Imo i would change the booster first and re-evaluate the issue. Anything jimmy rigged on anything safery wise is never a good thing.
1996 Mustang GT, 17x9 front and 17x10.5 cobra r replica rims, 255/40/17 front 285/40/17 rear at the moment,
o/r x-pipe flow master 40 series dump downs, cai/ram intake, 75mm c&l throttle body and plenum, pi heads and intake swap, msd wires, stock gears, untuned at the moment, no dyno numbers for now.