I used to own a couple of 5500 balers. There is not a lot you can do to increase tension on the bale. The tension is all in the springs. Even if you could put more pressure on, the 5500 is not a particularly heavy built baler in the first place. Whatever you gained in firmer bales would be lost due to increased bearing replacement/belt repair.
Not saying the 5500 is a bad baler. The 5500 is a simple machine, easy to operate and work on. Parts are relatively cheap. Makes good straight looking bales easily in most all conditions. Just not the heaviest. The advantage is that you can get by baling at higher moisture than a newer modern baler that makes the bales much tighter.
I would compare the bale tightness and quality of the 5500 to the old NH chain balers. IMO, the 5500 made better and tighter bales that kept longer than the OMC/Gehl roller balers and NI soft core belt balers.
IMO, Hesston's mfg process was not quite up to par to keep all the rollers in a straight line. My 5500's were well used when I purchased them. The bars on the bale forming cage inside the bale chamber wore through on my first baler. Kind of a fatal breakdown. I used that baler for parts for my other baler. Came in handy when the main gearbox shaft sheared off. Also used quite a few parts mix and match.
I now have an 856A baler. I tell people it's like going from a model T to the starship Enterprise. I could fix most anything that went wrong on the 5500 in my sleep. Seems there wasn't a week went by that I wasn't splicing a belt or replacing a bearing.
I'm afraid when something goes haywire with the 856A, I'm just going to pull it to town and let the dealer have at it.
