Hi Jbwok,
I've been watching yours and StuartC's build logs having started Warrior myself, having looked at the gap between frames I've started in-filling below the main gundeck between frames with balsa blocks to get past the problems your facing. As I have a way to go and haven't started planking yet it's too early to draw a comparison or if to know it will work. I'll try and get round to a build log over the Easter break so there is another approach to compare. I'm also looking to open up the citadel and rig it with the 68 Pounders and the Armstrong guns, and leave a semi open upper deck so you can see the detail.
One problem I have found is that the kit supplied 110 PDR Armstrong guns are 4mm short at scale when compared to the detailed drawings Lavery has in his book HMS Warrior, so the scale is off. Aesthetically for the 2 upper deck guns I don't think it will matter, but I could come up short in the citadel if I replicate the kit guns as they will hardly protrude through the gun ports.
Gary