The first task was to cut the compression tubes to length. So I measured and cut them to length.
The next task was to drill the two bolt holes through each end of the compression tubes to match the holes already drilled in the brackets mounted to the wing. Fortunately, the rear bracket allowed access to measure for the hole. The front bracket under the leading edge skins so there is barely enough room to even get the bolt in. I put the tube in place in the bracket and used my punch to mark the drill point. I drilled the hole oversized to allow for adjustment. I flipped the tube and placed the newly drilled hole in the front bracket and put the bolt through it to hold it in place while I marked the rear for drilling. Once drilled, I put both bolts in and verified the tube could freely move allowing adjustment. I then repeated the process for the outboard compression tube.
Once both tubes were cut, drilled and bolted in place I was able to set the tank in place to begin the leveling process. This is where the directions were lacking so I reached out to Chris Wallen of Wallen Aircraft to ask for some help. Here is his reply...
"Making the fuel tanks level is not really that important. The dihedral of the wing will allow fuel flow to be carried out just fine. The main concern is trying to mount the tank in a stress free way so you don't end up developing a crack down the road.. What I do is just shim the square fuel tank mount tubes all the way up and then lay the tank in there and see if the angle brackets lay flat all the way around. most of the time this works and I can just mount like that. If there is a corner that is not laying flat and is to far off just adjust the square mounting tubes accordingly with the shims (washers). I adjust the tank all the way up because the bottom of the tank will rub on the 1/2' round tubing that you put in underneath it. Also make sure to line that 1/2" round tubing with an anti-chafe tape so it doesn't rub through the tank over time. The tank always is riding on that bottom tube no matter what. Put the clear anti-chafe tape on it and the bottom of the tank is usually bowed down a little like you said. If you can easily push the tank down to close that gap up it is fine to go ahead and just bolt it down. If it puts it in a bad bind you can always make a couple aluminum shims to go in between the tank and the mounting tube."
I also posted on the Just Aircraft Wings forum and got some additional advice...
"There should be a strip of rubber between square tube and tank flange. Punch bolt holes in rubber larger than bolts and super glue down. Drill holes for tank bolts where you can reach them through flange holes. Use washers to raise tank so it is above the bottom of wing rib."
So, after raising the compression tubes to the max level using washers as suggested, I set the tank in place to check fit. On the inboard side the flange rested on the compression tube perfectly with no washer correction needed. On the outboard side, the flange remained about 1/4" above the compression tube throughout its length. I think the bottom of the tank is bowed out just a little bit which is causing this gap. I can easily bring the flange and tube into contact with a single spring clamp (not much force). As Chris suggested, this is not a problem and the tank is good to bolt into place. I will however, add the rubber gasket in between the flange and tube as well as the anti-chafe tape on the bottom of the tank and 1/2" tube just as a precaution. Interestingly, neither of these suggestions are in the manual.
