I’m dealing with this gap issue with my new waterbox as well. I have the 110.4, but I believe all of the new models come aluminum with to top platform, just the frame. The leveling mat could arguably be compressed in certain areas from shipping and resting on other surfaces.
The stand’s build connects the 2 side walls with 4ft bars between, then you have the middle supports. Statistically the are imperfections in the “level-ness” of the bars, and the mat is supposed to accommodate. However, my back right bar has what seems like a design flaw, because it is slightly angled. That imbalance makes it a nuclear war trying to level the stand after putting the tank on.
Like
@RaymondL and others have mentioned. The logic/science doesn’t make sense on the weight distribution.
OPs gaps would change from adjustments to the leveling feet but then he’d be arguably unlevel. A better design would have been to make a solid, one piece, leveled rectangle top frame to rest the tank on, connecting in 8 places promotes unnecessary push and pull, raising and lowering connected pieces when tightening. The screws to assemble these are not typical, so you can’t keep them a little loose and adjust while all connecting, like other assemblies.
Anyway.. I don’t feel comfortable moving forward with the setup. My tile floors are a little unlevel, but the feet adjusted for it, before the tank went on. This is something that would need to be handled over a phone call, not emails. I’m waiting to hear back from Waterbox, so we’ll see what they say. In other words, I’m glad you got resolution OP, didn’t mean to hijack your thread, but it seems to be an ongoing inquisition over this leveling for a few. It may be ok today, but long term, uneven distribution is a recipe for disaster, to floors, furniture and livestock.
Here is some more pics of mine. Green, support. Red, no support. Adjustments to the leveling feet changes the red/green, but never found any balance. Envelope slips through with ease. I’m looking to get some upgraded leveling feet, but need more details.