Hello Tylor Jaxon, welcome to the DOW.
Let me address this a different way for your goal of variable adjustable run times with larger/smaller hopper capacities.
Bare-in-mind this is based on my different systems operating experiences.
I lucked out that the very first wood gasifiers that I ran were GEK II’s. These had an internal small capacity “Experimenters” raw wood fuel zone. So you could first play around with different fuel types stocks. Then you would add on a ~25 gallon quarter can fuel hopper. Surprise. Surprised. With the only ~1 gallon internal fuel zone many different fuels stocks would work.
But . . . once you added on the extended run gravity feed tall hopper . . . only a few fuel types would give continuous use! Chunked, low ash, very dry No Bark woods. Or coarse screened chip/chunks of the same.
The problems? Fuel particles goo glueing themselves and NOT falling down to self feed! We call this bridging/tar capping.
Many, many have tries different mechanical interventions to make the fuel particles fall&flow. Hopper&system vibrators. Rotating arms and plunger rod “agitators” and “breakers”. Pre-charring (torrifing) the fuel particles. Produced gasses hopper heaters/fuel-warmers. Fuel particles augured-in feeds. Etc. Etc. Etc.
I fall into the category of those just accepting that a smaller fuel loading is actually easier in preventing these problems that trying to fix for them later. For me, ain’t so bad to have to every hour/2-hours refuel to get you back looking at the system for problems.
Wayne Kieth himself once a large hopper-man now uses smaller hoppers and says he looks forward to a 1-2 hour refueling stopping driving break to be able to get out and stretch his old bones. Walk off the sitting stiffing ups.
On your system sectional sealing go to a large hardware store and look in the woodstove section at the rolls of woven rope bulk fiberglass door and fire-viewing glass windows sealing material. Make your system to accept the largest diameter available (usually 1 inch round). Don’t need precision ground flanges to make this stuff airtight work. No even precise ground out tongue and groove joints. Ha! Look at the airtight woodstoves and it is just either rough castings or flat plate with some spot welded on rope-groove edge retainers.
Trick is you want that rope to be compressed ~50% with then edge/post mechanical stops to not over compress or system use vibrations squish out and damage-gap/leaks.
A to-be-safe engine sucked system will pull together and seal better when in engine operaton. Engine NOT running/sucking down is where you want to watch for gasifier leakages. And the problems of system leakages.
tree-farmer Steve unruh