I have lee jr's with the wishbones, they are the 18inch spread model I believe, and look great on the boat. They do make passage forward a little tougher, but to me they are easier to maintain and I think they personally are more durable and easier to use. I believe my poles are 18 or 19ft, not sure off hand, it would show on the Grady catalogs on their website, I think 18 was standard through. I have mine double rigged and also added a center rigger, we troll 8 rods off my boat when conditions permit. Personally I've used hardtop mounted riggers and on an express or walkaround I'm not a fan of them, on a CC that is different due to space and mounting locations. I like having my halyards low where I can reach them instead of off the hardtop, on a 265 they are tough tto reach. I double rigged my center rigger and those lines are tough to reach, but I rigged them so you can unclip them and move the line to the center of the boat and reach it better when moved aft to attach to the clip and deploy it, then reclip it, keeps you from standing on the gunnels like you would have to for a hardtop mounted rigger. I also feel the lee jr's flex less due to Grady's holder's they incorporate on the hardtop, they are a lay down accessory on the site, I think they are roughly $150 a pair, I was just on lee's site today ordering parts for my hardtop rod holders.
As mentioned above, the hardtop will need a bit of reinforcement to do it right, and in the end the lee jr's will end up beng cheaper to install. For a serious offshore fishermen a wishbone would be perfered over a hardtop rigger anyday, I don't think I'd ever get hardtop mounts unless it was on a CC.
