Looks the goods. Simple but effective.
The anti scalping wheels on the front could be a good idea.
Wheels at the front would mean that you would need to hinge the drawbar, that would make it more complicated.
I did think of the Greenfields walk behind i have here, its got one single castor type wheel at the front. That might make stability issues.
Not sure how you are testing it Greg but ive found there are a few people around that mow grass to a 10mm height and leaving it any longer, 'well its just not worth mowing if your going to leave that much grass'. My dad is one of them. No wonder the ride on chews belts, its as max capacity for the engine power delivery more often than not.
My only question with the tow behind slashers or your new 'side to side and right behind', is how do you know when the thing konks out?? Well other than constantly watching where you have been to see the grass is as long as when the slasher went over it.
Whats the saftey implications as far as it being a constant tension drive belt? Should it have a clutch and a deck brake???
Thats one fancy prototype. Where it mine it would never be painted, id have to test it to death before i was content that it was finished and worth of a coat of paint. lol.
I had thought of doing something similar but more converting a rear engined ride on mower into a walk behind slasher.
Thinking about it that might be a good idea to build soemthing similar for my dad. That way he can use his Ranger out in the rough stuff and mow an extra Colt deck width.