States vary as to laws regulating widths and lengths but most importantly required permits for wide or over length loads.
First with a three axle trailer, do not attempt to turn sharply as you will eventually cause
the steel in radial tires to separated. I assume you have a spare on the rim.
Of course the width has been mentioned as states vary for example it is legal in NC for loads up to 9' 11" are legal during the day without a wide load permit needed. Generally other states will accept what is legal as long as the tow vehicle and trailer are both taged for the same state but as to width, not sure. I would highly suggest that you contact the states that you are going thru as you will have to have a wide load permit per state.
As for overhang, again it depends on the state. Generally anything with an overhang of 6 feet from the back on the trailer has to be flagged or lights. Some states will not allow anything over that at night. What you have to be very careful is the over hang of a mast on the rear. Although 6 feet I was fine but a couple of more feet, the cops never bothered me but did once when the overhang was 14 feet. Again it will depend on the state you are going thru as to their requirments.
Again states vary but most will require with a permit in place that you have to go thru the weigh scales. I can attest to that being stopped a time or two.
As for the straps seen in the photo, I would highly suggest that two more be applied to keep the boat from shifting forward or backwards and trust me on this as I have seen it and experienced that in the beginning as a dealer. Take a strap around the forward cleats and come backwards. Take another strap from the stern cleats and go forward