What volume did you put into your fermenter? I imagine you should be able to ferment 5.5 gal without issue. To be accurate, 1 gallon weighs 8.3 pounds, so fill to 45 pounds as measured on a scale.
If push comes to shove, use a blow off tube...
I use ferm cap drops to cut down on the blow off. I have put 6.5 gallons in a 7.5 gallon sanke as well as 13.5 gallons in a half barrel without the need for a blow off.
Despite using ferm cap I have still had some blow off through the PRV a few times. The PRV that I use is plastic and can't be taken apart for cleaning. I had to replace it once after I got beer in it and it got clogged. I built a blow off catcher from a water filter housing and a piece of tube I cut off of a sanke spear.