Long Term burn for RMH kiln

I have been experimenting on how to get longer burns out of my RMH for our kiln. In other words, bigger wood hopper. I am making progress for sure, but I was curious what others have tried. The wood is outside and so is the burn chimney (the 55 gallon barrel)

I have found my making a air intake the size of the intake below, I can load up wood and then cover the top. I have to put a grate in place though or the wood will plug the hole. One work without a grate is to make an air intake closer to the vertical chimney area, but I am trying a grate today. Since I have two units, I have one working normally, and then a test one. The test one is now up to 2 hours without refilling, compared to 45 minutes for the original (often only 30 minutes)

We tend to burn 12 hours a day.

Where do you put the grate?
I am totally new to RMH's and have plans to build one later this year to heat my animal outhouse. A longer burn would be very useful as the place is very drafty (it needs to be as there is a lot of moisture coming through the old soil floor) and sometimes we are only there for a couple hours before going home (we live 10 miles away).
A longer burn would mean more heat for the goats which would mean I could have them kidding in the winter. At the moment I can only kid them between May and September because of the harsh weather up here. As I have a waiting list for kids already for the next 2 years I could actually make a bit more money if I could increase my herd and kid them all year round.... so I am very interested in your project.
I have played with the idea of cutting sticks into 5cm pieces and add a large conical shaped wire mesh basket to the wood intake chamber to feed the RMH for longer. This would work a bit like a pellet feed. But as I never built or used a RMH I am not sure if it would work or what other adaptations it would need. Presumably there would need to be a space for air intake, so the basket would have to be slightly smaller than the intake space.
Am I making any sense here ?