Not the best picture ever, but I’ve got my DMR tensioner pushing upwards, and it works a treat (I am using a half-link chain tho’).
I’d go with the suggestion to add a half-link and then running the chain over the tensioner.
If you get with SS’ing, the Surly steel rings / cogs are great (in my experience), they are thick and have usefully long teeth, and if you are obsessive about chainline (and/or want some colour in your spacers), the every useful VeloSolo people have a great spacer kit, which will allow much finer adjustment than the DMR kit (which comes in an assortment of colours).
The chain doesn’t need to be crazy tight either, just tight enough – some give in the system is necessary (although this can be a very fine line, looking at some people’s pictures online 😉 ).
Ah, one last thought – tho’it might not be relevant, but the DMR tensioner doesn’t ‘work’ with forward facing semi-horizontal dropouts, but I’d be surprised if you have a MTB frame with that kinda dropout, as it’s more a road bike thing.