Some variables here but 5" sounds like a lot of travel, also most camper tensioner when adjusted run about #300. I'm assuming the fastguns being used are the add on shorties? Derringer? Just curious, unaware of fastgun with no spring.
Our original set of torklifts tie downs used the chain & manual turnbuckle, spring was in a lil 3" can bolted to mount arms. Our previous Happi jacks used the tubular turnbuckles with spring inside, like current full length Fastguns. Using the fastguns, the spring load 'cans' are removed from mount arms.