So I glued on 3/8" I beams. I also had H beams but it appears the real ones are the I beam shape. I have used 1/2" versions. I used what I had here. I fear the longer engine might need more travel space. I only glued them where I think they'll remain after the fuel tank gets mounted. I cut them roughly to length leaving extra in case the tank dimensions aren't perfect when I make it. I also leave them long where they'll touch the pilots that aren't even designed yet.
It's tuff to get things perfect without designing everything in advance. Because I wing it on the fly, I went ahead and mounted the trucks so I can see where stuff needs clearances. I only make one of each type of engine so there's extra work as models change.
It looks ugly to some? For me, I can see the finish line even when I start. As the engine develops, you'll see what model it is.
