Have you seen how Seagull does their 54" Ultimate compared to the Goldberg? The strut on the SG is a little wider on top and bottom and the "bump" slides into the strut instead of the strut sitting next to the bump. It is a little cleaner look. The strut would need a little redesign but the finished product is worth it if you are as picky as I am :-) .
BTW 1/4" ply is WAY overkill in this area. 1/8" is more than enough. 1/8" ply off the shelf is already a lot stronger than the lite ply supplied with the kit, You will be adding weight you don't need IMHO.
David