So, we use ratchet straps on strippers, Kevlar and w/c. Considering it is mostly my Swift that gets loaded, I do crank it down until the belly distorts slightly. My 2x4's have carpet on them for protection and if I get the tension correct and shove the boat it does not move on the rack. If it moves, I'll go another notch. I doubt I have ever gone too far, never heard the boat groan or crack when adding tension. I also cut off extra strap, so the ones meant for boats are sized accordingly so there isn't excess strap to secure some how. I just find them easier to use. I'm the paranoid type so security is important.
When we transported the two w/c boats back from Geraldton a couple years ago we also used the ratchet straps and again, tight enough to just distort the hull. Mind you with two boats on the longer 2x4's I have to walk up the hood of my Highlander to get to the eye bolts in the middle to get the strap hooks on. Considering both those hulls were rather old and lacking canvas and a lot of support structure, we had no issues on the highway with passing semi's for the 1000km drive back to Manitoba.
I know some don't use bow ropes at all and likely see mine as overkill, but on a return trip several years ago we drove into a storm front and despite the nose being roped down tight, the bow shift 6" sideways when we hit the front wall of that wind. One advantage of the nylon straps over rope is they don't stretch if driving through prolonged rain events. The bow ropes do but I have to be careful if I tighten that when they dry they shrink.
Ultimately, whatever works for each of us is the right way to do it. Much like the innie/outie debate except if you do it wrong in this case you may be shopping for a new boat.
