I dont see an issue with you not being able to put the butts on top, that spacing will be ok...remember flip the racks upside down and your getting 5/8 of an inch back on the spacing. I am not going to have that issue with 7 inches for the top two and 5 inches on the bottom two if I am going only large meats. I will always cook my chicken on my green egg, its produced what I want and what as won me awards. With the spacing I mentioned to you above, my main point was to be able to have all 6 of my racks support full size pan height spacing. With the 3.5" that is going to be likely the minimum id consider going with, it will leave a 1/2ish of spacing. My other concern was to have a smoker that I was able to have side by side pans, the 27 1/2 inches was huge for me with inches to spare not touching each other and the metal sides. I understand your concern on moving it up and down, ive talked to others and it still doesnt seem to be an issue especially if the rise on the trailer isnt more than 20 degrees. When I plan to get my enclosed in 6x12 or 14 I will use solid blocks at the end of the door and just roll it out on the door to sit, at least that is my plan. Will see as I dont think the weight will be exceeding anything if the door is on blocks, I havent read anything that concerns me there yet.