Framing a Moonboard with 2x6 instead of 2x4 to avoid having to put in crossbeams?

With Covid 19 shutting down all the gyms around me, I've decided to build a Moonboard in the garage. I've been reading the old plans provided by Moon here: https://www.moonclimbing.com/moonboard/downloads/MoonBoard.pdf
In it, they stated that they used four 2x4's spaced about 70 cm apart with 2 crossbeams in the middle of the board to provide support. I don't have too much construction experience so I was wondering if I could simplify the design by using 2x6's instead of 2x4's to eliminate the need for crossbeams. I've been reading a lot of woodie construction threads and it seems that this is a popular decision. Just wanted more opinions on if this is safe and fine or if I run the risk of warping the wood when I climb on it without crossbeams.

Yea the instructions that come with the Moonboard are crap. It will fall down if you build it that way. No point on trying to skimp on framing materials - the more solid you build it, the less it will move and flex and whatnot as well. I built mine with 2x6's on 16 inch centers and still added crossbeams. I also bolted my kickplate frame to the concrete slab below. Board was super solid. One thing to take note of if you are also planning to install lights (highly recommended) is that the gaps between the lights are designed to only reach over 2x4's, so using anything thicker than that requires either drilling holes in or notching your studs at the crossover points (at the top/bottom of each alternating row). I recommend notching so you don't have to pull the whole damn string of lights through the hole every time. It's annoying to do once your board is already up (I didn't realize that until I started installing the lights- got two rows done then realized that my lights wouldn't fit over the stud so I had to notch them in situ, which was a pain since the crossover points are either right next to the ceiling or right next to the wall at the base). Seems like it would be way better to pre-notch the studs prior to installation. You should only need to take out around 2 inches vertically, about an inch wide. I also strongly recommend using brackets on all your stud ends (which I also don't think they recommend).

Hope this helps. Remember: measure twice, cut once. 

One more thing - in addition to the crossbeams, you can easily build a shelf system behind your board, which you can tie into the ceiling and/or wall behind the board - this adds additional stability to the frame while also providing a ton of room to store stuff. 

Sorry last thing - I used 2x4's for my crossbeams so that the lights could easily fit over them. Just didn;t seem worth it to use 2x6s and have to notch every single one of them. 

If you have the room I would frame it in 2x8.  I did mine with 2x4 but would have done 2x8 if I had the room.  Mine flexes a bit and I'm pretty light. 2x6 will be good but 2x8 wont flex at all. 16" centers are a good idea too, just make sure you don't land on a bolt hole layout (or near one) when you layout your studs.  feel free to dm me if you want advice, I'm a carpenter.

I did my Tension board with 2x6 douglas fir 16in (roughly, as I tweaked it a bit to avoid the nut holes) on center with the sides, top and bottom doubled, and 3/4 birch plywood. It is bomber. It's also very heavy, which was relevant because it's adjustable and so needed to be moved around a bit after it was assembled. Fairly sure I couldn't have dealt with the weight with less than 4 people if it had been 2x8.

Chandler Van Schaack wrote: I built mine with 2x6's on 16 inch centers and still added crossbeams. I also bolted my kickplate frame to the concrete slab below. Board was super solid. 

I'm assuming you used six 2x6's then to frame the board (with 16 inch spacing) instead of four?

Michael Yu wrote:

I'm assuming you used six 2x6's then to frame the board (with 16 inch spacing) instead of four?

Correct.

I used 2x6 on 24” spacing. It’s tied directly to the ceiling, so my flex is minimal. If I were so to do it again, I’d go on 16” spacing for two reasons.
1, insulation is cheaper and easier to find
2, I wouldn’t have to add some bracing members at the 4x8 seams.