BTROUSE...your questions have mostly been answered, & you have done the important things. I will add a few points.
The weight of these rigs is quite small, even so, just make sure you have some tongue weight. The hitch ball is designed to mostly hold a compression & shearing force, the weakest part of the setup is under negative tongue weight, pulling upwards on the ball.
How ever you tie down, stop & check them after the first 20 miles, then again at ecah gas stop. The boat will "wiggle down" from its initial tie down. The amount may be negligible, or it might be lots, or a strap might fail. When I towed mine home, 1 herc strap was 2" above a safety line. Wind loads lifted the safety line enough to just touch the herc strap & it frayed in 1/2 after only 50 miles. The rule, check often, & feel the wheel hubs for heat as soon as you stop. I used 6 tir downs, 2 on each side, 2 across the top. The sides work like spring lines, one from stern of boat forwards, the other from front bar backwards. This prevents fore/aft movement. Preventing forward movement is critical, that is what the boat wants to do every time you touch the brakes, & you might have to panic brake at some point. Ties holding the boat down should not be cranked down, you will damage the hulls. The spring lines do all the work, the tie downs only hold the boat from bouncing up when you hit bumps.
I would slow down, from 100kph, to 90kph. (61mph to 55mph for our American friends)This will save gas & give you more reaction time. Of course drive more defensively than normal.
I was surprised at the air load. I towed with a V-6 van, & it kicked down a gear at even slight hills, & 2 gears on the tougher pulls. Gas consumption was noticeably increased.
When backing up be aware of those long hulls. If you get the car on enough of an angle you can contact the hulls with the car body. Also be aware of the arc the mast will travel when making a turn. If you make a sharp turn the mast will be 5' to the outside of the car, unlikely at highway speeds, but a consideration while manouvering.
Finally, these boats are wide, you will see the hulls well outside of your car. Keep the car tires on the "grooves" in the road & you're OK. If you were to drift the car to the centre line, or let the trailer move inside,(during a left hand curve) the hulls can easily be in the other lane. Combine that with the other guy drifting a bit towards your lane & it could really wreck your holiday.
A few notes on bearings. Fresh water can be just as damaging. The hub assembly heats up & expands the air inside, causing some of it to leak out. When you immerse the hub in relatively cooler water, the air contracts, creating a slightly lower pressure that results in water being drawn into the hub. This eventually spells disaster to the bearing, hence the failure of bearings with few miles on them.
Google "changing a bearing" just to get a visual on what to do. It is a simple job, but the first time will take much longer, you may need help, or just the right sized drift to push the races out if they are in bad shape.
Finally & MOST IMPORTANTLY, proper packing of the new bearing, or repacking the old after cleaning it thoroughly with solvent. Never spin a dry bearing with compressed air to dry it. It is not enough to just woipe grease every where, the grease must be "packed" into the two halves. To do this wear surgical gloves,(they are dirt cheap & make cleanup a snap) place a good gob of grease in the palm of one hand. Hold the bearing in the other using your fingers, as if you are trying to push the 2 halves apart. Try it, you will see the halves separate slightly. Now snap the bearing down into the EDGE of the gob of grease, this will drive grease up in between the halves, do it a couple of times...you will see grease extrude from the other side of the bearing. This is what is meant by "packing". Rotate the bearing in your hand & do the next spot...continue around the circumference. You will find the job much easier to do than to write how to do. Finally resist the temptation to fill every available space with grease, to much is not better. The engineers can explain why, but essentially most of the grease has to get out of the way as the rollers turn.
Most trailering SNAFUS are due to bearings and/or tires. Tires get weak after time/sun even with new looking tread. Those small tires also use quite a bit more pressure than your car tires. Sounds like you have been diligent, enjoy your trip, I'm jealous...no sailing here for the next 4 months.
--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--