I don't post here much because everybody else knows a lot more than me so I mostly just lurk and learn BUT in this instance I think I have some insight, to wit:
I haul my 260 with a V6 Nissan Pathfinder.
My introduction to hauling it was when I picked it up at Sag Harber in the Hamptons from Moe & Joe the "we don't know 'nuthin about no sailboats" marina owners who I had paid $400 to package the thing up and load it on the trailer, both of which they did as badly as is humanly possible.
Anyway, we hitched it up and brought it back out the LIE (I would have loved to use the Parkway but alas the mast won't clear most of the overpasses) at around 4 PM and hit NYC where we learned that there'd been a fire and explosion on the bridge we had painstakingly researched and decided upon.
The engineers had reduced the allowable load for that brdge and while we were well underneath it they didn't believe me. Hell, looking at that huge thing we were towing I wouldn't have believed me either.
So they shoved us off the expressway onto a side street in the Bronx where we drew a lot of odd looks trying to navigate around narrow one way streets. A good way to learn all about towing a bigass boat like a 260 while trying not to throw up.
Anyway we found the Tappan Zee and made it back to Central Pennsylvania about midnight. We were thoroughly fried and five minutes away from a divorce but the rig did just fine. even through the torrential downpour/thunderstorm we drove through for the final hour.
A month late I took it to Lake Champlain, around the north end and down into the Vermont Islands (Isle La Motte actually) a seven hour drive. In August. She did fine, although be advised that the rig won't fit under every gas station canopy. You have to pick and choose carefully.
Did I take it pretty easy? You bet your sweet butt I did. Don't think I ever went over 62, and I watched the temps like a hawk. It was a rock back there.
Bottom line, don't be dumb and you'll be fine.
As far as the ballast issue, not a problem at all.
I'm going to skip the "open up the valve and let the water out before I hit the ramp" thesis because I'm certain that by now you've seen the flaw there and so we'll assume that's a non-issue.
But as noted above it does not take very long for the water to drain. Frankly, I've seen a good many juiced up weekend warriors in 18 foot power boats who took twice as long accomplishing a retrieve as we do and I'm no genius.
The only thing I will do is if there are a number of boats waiting on a haul out I'll pull over and let the crowd disburse a little, but I'd probably do that anyway.
And unless the ramp is pretty shallow I can usually haul it out without having to extend the trailer tongue either. Get it through the goalposts and tied up to the winch and just pull it out so the ballast valve just clears the water. Six inches is plenty if you're worried about it.
(Plus, as people have noted previously, the rubes find it endlessly entertaining and stand there fascinated watching the water gush out. A great conversation starter, assuming that you want to talk to a dead drunk guy with beet red skin who smells like dead fish.)
Bottom line it's just not an issue.
Good luck and let us know how it goes. Mike