Scot trailer set up

I have an Tee Nee trailer circa 1988.  I know the Scot is mostly supported by the keel.  My trailer has FIVE rollers down the middle that the keel travels down.  The furthest back is just to guide it while loading.  There are two larger semi-clear ones on the front and the back that the boat rests on while loaded.  Then there are two smaller black ones between those two.  My questions is about the two smaller black ones.  They are aprox 2 inches lower than the bigger ones and therfore don't support any weight while the boat is loaded.  The hardware is tight and it looks like they have always been that way, and not just fallen down.  Are they supposed to be that way?  Was it just set up wrong?  Seems to me that four support points are better than two.

They keep the bow on track and not hitting the trailer until the boost gets to the second big roller.

When I load my Scot, the bow stays up without ever touching the middle rollers.  It might come down in time to touch the furthest forward, but I'm not sure.  I will pay close attention next time.  Even so, would it hurt if the middle rollers supported the boat?

If the ramp is steeper, or the trailer is in deeper, the bow may touch those middle rollers. I usually only put the trailer in far enough to just get the roller that is all the way at the back of the trailer to touch the water. If those middle rollers touch the boat while trailering, it would seem to rub on the gasket. My TeeNee trailer is the same.