mounting rod arch - acceptable backing plate?

[McGillicuddy]

I'm thinking I'll mount an aluminum rod arch on the Seafari this weekend. It has a 2" wide plate for the base which will be mounted atop the ridge cap immediately aft the side windows with 4 or five 1-1/2" x 1/4" s.s. pan-head machine screws with s.s. fender washers and nylocks on the underside. I was thinking I'd use 1/2" thick polyethylene strips(think cutting board) on the underside of the cap to better distribute pressure on the cap (keep in mind the inside width is only 1-1/4" and 4 or 5" deep so proper coring will be tricky at best). Is that foolish or can I do that with out losing sleep.

[PressureDrop]

i have rectangular aluminum backing plates that i fabed for my top that mount under the gunnels 1/2" thick not positive on the dimensions on them but i want to say they are 8" by 4" (or however wide the gunnel is), ill get some pictures of them one of these days, anyways, i wouldnt use anything but aluminum

i bought a slab of 1/2" aluminum that was 4" wide (forget how long, but long enought for 6 backing plates) it em with the chop saw, marked the holes and over to the drill press, took me a good day to do all 8 but totally worth it, and throw some locktite on the bolts when you put the nuts on

[Old'sCool]

I used 1/4" thick aluminum on all my rod holders. I think you would want at least that given the load they could see. Starboard type materials have a tendency to crack under uneven compression especially near hole locations.

[fdheld34]

Gillie--
I used 3/4" marine ply and topped it off with a 1/4" piece of aluminum for backing plates underside for mounting my outrigger bases. I still get flex when outriggers are deployed (15' Telescopic aluminum). I think you would be correct in constructing some type of longer backing plate/load distribution (fore to aft)..especially for an arch. Obviously tower/hardtop has more than just two contact points so probably more rigid overall and would require less. Might use your starboard type material in combination with aluminum to create longer backing???
POST SOME PICS!!!!!!!!!
-FRED

[bigeasy1]

Gillie
I mounted this arch on my Tsunami,and although it's mounted differently than yours will be,I used 1/4" aluminum backing plates.
They were only about 4" in diameter.I can hang off the arch with no deflection or movement of the arch or glass

[McGillicuddy]

Thanks for the feedback guys. I was trying to avoid the aluminum contact with the stainless screws but maybe I can slip some nylon washers in there. I guess Stainless backers are fine, too, if a little heavier... Your arch looks awesome John123. Your Tsunami is incredible. I'm working with a pre-owned arch that will offer functional utility and little more - but hey, it cost me a case of Stone Pale Ale...