My term for lack of better. The lack of lower gears as most single rings off road range say 32-38?
A bike using multiple rings can change to a lower gear to compensate for rider\bike weight and grade of climb =spinning.
Mashing, the use of weight and leg strength for climbing is harder on your chain\drive.
A single ring bike rider will be mashing more often as he can't gear out the 'load' to an easy spin speed.

I won't usually change a gear when climbing -hard on the drive if the chain\drive is under stress (load).

Now, spinning versus mashing-

Climbs long, not too steep:
A spin sitting in the low gear -30T cog will work, but slow.

Climbs shorter\ more extreme:
The gearing I choose is 24T as the point where the bike slows after the initial run at the slope, you must be able to keep the speed up to overcome inertia and spinning fast then catching the drive/chain as the bike slows = is harsh.
Mashing in a higher gear works better as you can stand on the cranks climbing and muscle the bike up.

Short climbs with near vert\vert tops:
I choose a higher gear again as I will not spin up, simply power run @ it and when I get to the top, I have to rotate the wheel froward quickly as to not fall back\inertia =using less teeth rear and rolling forward with a half revolution of the crank compared to a full rev using the 30T cog.

I'm doing 'climbing\trials' on a 21 lb XC bike. I'm a light guy, I worry about the stress I put on chains\rings. I'm glad to see more print of 8 spd being able.
Most people I've read snap the chain -do it climbing, And with the ability to 'gear out' and spin.

Cross chaining is suspect (gotta love those single ring bikes eh? No brainer, no cross chainer!)

I'm using the upper roller on the boomerang as a tensioner to keep the chain on the ring.
Also , to not have any derailer movement\shift out as I hammer these hills. The drive must engage smoothly and when I stomp on it.
I think these systems are MX derived chain tension pulleys for constant drive engagement for rear shocks as the flexed rear leaves the chain slack?

Kinda happens with the bike derailer if it moves during a jump or abnormal chain tension shift.
Kind of a chain 'wave' that lifts it off the top of the chain ring I think.
The lower pulley can be used to stop this, upper for the constant drive engagement with rear suspension.

I will build an 8 spd drive when this 7 spd hub\wheel gets wasted.
Main reason =no nice body 7 index shifters.
I wreck them 1 per year.
My drive will stay 11-30, the range is all thats important to me, and less clicks to get to across the better.

I can't say yes or no to 9 spd mono-ring drives as I haven't used one.
Glad the bike works fine. Many of the points may not apply, most people don't seem too into climbing.
Gravity, DH, maybe freeride =no problem. Climbing makes me want to post a caution.
Yes i'm paranoid ...as a guy who relies on his gear to keep him safe and continue having fun.
Safe than sorry..you know.


Wow..what a long post.