precisely, i believe i've started thinking about it a little before your 2 bolts presentation, it just re-inforced my idea more. i mean the slider bolt alone MIGHT be sufficient in some applications, (people who like to pedal for some reason, as an example) but you can't compare the force of pushing something, against trying to squeeze it with both hands. as i said one of the slider bolts is now broken, so even though the rest of them are tight (i can't even reached properly the ones directly under plate, because i have a double kickstand in the way, so it would be nice if you could some shorten cover plate a bit) , i went out for a ride, and the chain should have gotten loose almost right away judging from previous occasions. it didn't. it's a little loose.
another possibility is to place an additional "pipe" like this thing (the upper part where the bolt sticks from, only yours would span across the width of the upper and lower plates, you could have it connected with slider slots as well with bolts both sides to lock it down, the m8 adjuster bolt would be driven all the though it but not stick out the other side . you would have one plastic part from side to side on the motor sliver bolt housing , with a little round insert to have that pipe pushed against it.
think of it like it's a big giant shovel in a tractor pushing sands.
right now i can't even remove the secondary bolt if i wanted to , it's gotten itself deadlocked with the bolt i placed instead of the carriage bolt. so i'm kind of stuck in jdevo's place
so i'd really appreciate it if could sort it out with bigger bolts AND 2 adjuster bolts, i mean you can place them the same way i did, and give the user option to add it only if they encounter issues like i did. but just using bigger m8 bolts, might prevent from my kind to snap them, but i don't think it would prevent it from sliding back.
the second biggest issue is the twisted jack shaft in the upper sheets, because of the teeter-totter in the upper plate i can't adjust the jack shaft equally , so now the pulley is positioned in the way you saw that forces me to use spacers, however since the belt tends to slip outside a little it may still rub against the mud guard.
oh btw about the guards. the right upper sheet adjust bolt have gotten pretty good at catching my pants when i try to start pedaling.