Looking for some concave for your flat decks? 
This thread may help you out.
INTRODUCTION
I recently did some research into concave pads for my MTB and decided to summarize it for the people interested in this topic. Also made a video on them: Mountainboard Concave Pad Installation - YouTube
There are plenty of people who use (3D printed) concave pads and really like the feel of them. Moreover, the Kaly decks which have aggressive concave on the edge are very loved aswell. So the main reason to use concave pads is wellā¦ you guessed it to create concave on a (relatively) flat deck. Trampa boards are pretty much flat along the width, In my case I often get foot fatigue during longer rides >15 km (especially on heavy terrain). I recently also joined a racing event at a go kart track, where skilful cornering is pretty much one of the factors to getting a good lap time. Here I think concave would also help out a little. Plus, I think a bit of concave just looks a bit better.
For comfort one might also want to look into MBS bindings since everyone here really seems to like them. I might buy a pair in the future.
CONCAVE PADS AVAILABLE FOR PURCHASE
Sabre Blades by @SabreDynamics
These concave pads flex with the deck and make it a bit wider as well, providing great carving and control.
E-toxx flaps
These are essentially aluminium concave pads which also extend the deck width. These have to be attached by bolts through the deck, also providing great carving and control.
Max Capps Imppants
Griptape implants to create localised concave on your deck.
Here are some threads I found which also include concave pads (might be useful as inspiration for some of you)
If anyone has more info please let me know
Beautiful pads made by @sebaszz. Maybe he can upload them on thingiverse for us 
Jonny1983 pads on @Sedmii ās build
Jonny1983 coffee smell concave mod by @taz
Griptape inserts/concave
THINGIVERSE
(my design) Trampa Concave Pads: Trampa Concave Pads by Creavenger - Thingiverse
Trampa HS11 Concave Pads: Trampa HS11 Concave Pads by Jonny1983 - Thingiverse
Trampa 3D concave extension: Trampa 3D concave extension by Koringer - Thingiverse
Prototipo concave:
Excluding the griptape inserts, all these pads were 3D printed. The best material to use imo is PETG. TPU or TPE is also possible, just like PETG it allows to be bent to match the camber (or rocker) of the board but it does allow the slightest bit of cushioning/deformation on the edges. Of course, this is also depending on print settings (my thingiverse link contains more print info).PETG will not deform when you press your foot into the materials, ensuring you can transfer the force to the deck.
You can also use PLA or other materials (experimenting is always welcome) since the pads are relatively thin and can be bent easily.
Concave pad design (advantages and experience)
I printed the available files on thingiverse in flexible filament on my Prusa MK2S.
I decided to print the Jonny1983 pads, which felt great just putting it on the deck and standing on it. I didnāt want to use the small nose/angled part for the deck, so they were just a bit too short and one side did not taper off.
Then I printed the carver pads which were way too smallā¦ should have checked the dimensions haha
A fellow forum member @starky_boi asked me to print some pads for him. We agreed I should make pads which are a bit longer and tapered on both ends. So I made a new model, the pad is 22 cm long and approximately 5cm wide. This will make sure the pads will not interfere with most top mount battery boxes. The pad can be used for both the left and right side of the deck.
He tested them without bindings and really liked them.
āThe added leverage really makes a ton of difference IMHO. It really does add the otherwise missing skateboard feel, and riding with bindings is now even more comfortable in long rides. I feel more in control and I feel less strain on the top of my feet as I donāt have to tighten the straps as much.ā
I have also tested the pads without bindings and they feel great, definitely more control than without pads. I also tested them with bindings and it really locks your feet in nicely and feels comfier for the bottom of my feet.
INSTALLATION
Epoxy method: Credit to @starky_boi, looks awesome!
Sand deck, glue pads on with epoxy and clamp them on the deck (optional, coat pad in layer of epoxy for extra smoooothnesss). One point of attention, is the use of epoxy, make sure you use a good epoxy because TPU and PETG are generally hard to glue.
Double sided 3M VHB tape:
Video: Mountainboard Concave Pad Installation - YouTube
Try to use very thin tape, otherwise you might end up with an edge visible through the grip tape, to counter this you could only use one strip of double sided tape on the outmost edge of the pad so the inner part of the pad sits flush with the deck. You could also go for the epoxy option or donāt press the griptape too much on this edge transition.
SUMMARY:
I would encourage using concave pads on flat deck mountainboards, since board control and ride comfort will increase. There are some options available to 3D print, which are easy to 3D print and pads like these are relatively easy to model. Additionally, if you have a mountainboard setup which is mainly used on streets, pads like these could replace bindings and still give you good control over the board and result in a cleaner look.
