Update: I never liked how the trailer axles sagged readily when on uneven terrain. It seemed unlikely that after only a few years of rust they would loose that much spring, but when backing down a crumby ramp with a dropoff, the tires would ride up so high they would rub the insides of the fenders.
So for my spring replacement, I went with the heavier springs. Yeah, it's a harder ride for the boat, but now I can jack up the front when I'm storing it, and that rear axle doesn't sag down. The wheels don't rub fenders on uneven surfaces, and I don't wince when I cross those train tracks in Little Washington.
Carl at Merritt Marine found the brake leak that nobody else has been able to fix. He asked if it had always leaked, and when I said yes, he bet me it was a loose fitting that was never properly tightened. From a dolly under the trailer, he called out he'd located it, and with a few twists, I was good to go. That's after my local marina came up empty handed.
I trailered to Smith Mountain Lake for the weekend of the 4th, and I'm happy to say all 200 miles was care free, and leak free - both ways! About time!