[tsubaki]

I've not read anything about "correct trailer setup" but I've made several boat trailers over the years, to fit each individual boat.
First, every trailer is different but there are a few rules of thumb.
The top spool of the winch needs to be at the same height as the bow eye. Too low and you are actually winching the weight of the boat down and not across the rollers.
Depending on the setup of the keel rollers (if any), all of them normally contact the keel when trailering the boat as do the bunks (again if any).
Tongue weight is supposed to vary as to the weight of the fully loaded boat. On the smaller boats, I normally have 50-75lbs of tongue weight, the setup on my V has between 100 and 150lbs of tongue weight.
Normally you position the boat over the trailer to have the best contact locations of the rollers for the trailer and boats sake, then adjust the winch stand to fit and then adjust the axles (forward or back) to accommodate the desired tongue weight.
Too much or too little tongue weight will produce a massive towing hazard of the vehicle becoming suddenly uncontrollable, usually when braking or when a bump or dip in the road is encountered.
I could not tell if your axle setup will allow adjusting forward or not. If not, relocating the rollers or even having to completely redo the roller system may be necessary after you have positioned the boat to achieve the desired tongue weight.