As long as they hold air I wouldn't worry about it.
I'm curious why you would need to run low pressure in the front tire? I have never had an issue with bead seal on any of my machines, and I think I run them low on pressure; but I also use correct size tires on them. I can understand your situation with the skinny fronts, but why the low air pressure?I tubed my Firestone tri-ribs because I had a hard time keeping the bead sealed at low pressure. They truly need a bit narrower rim than the stock 5.5". My rears I tubed because I planned to fill them.
I'd also tube if I was going to use slime as a flat preventive.
High or low pressure mine cut into the turf on tight turns. I had to have the tires taken off my rims and the little tits cut off and then sealed. slkpk12 PSI. I could run them up to 28, but they cut turf if I do.
Even though the tri-ribs are sized at 16x6.50-8, the 5.5" wide rim is too wide.