Maximum stove pipe length of Liberator rocket mass heater

I corresponded with a representative of Liberator Rocket Heaters to confirm how much horizontal distance it was capable of pushing the exhaust through. Their response surprised me, and I’m curious to know what those of you who have used them before might think! They stated that the Liberator was certified for only 12 feet of horizontal distance beyond the stove itself. The rule of thumb I’ve always followed with ones I built myself for a fifty-gallon drum and 8-inch stove pipe was that the system can handle 50 feet, minus 5 feet for each right angle.

For my current project, it would be much preferable (for code reasons) to install a Liberator rather than build my own, but it also would be much less effective for this particular use case if limited to 12 feet. So I’m wondering, is this just a case of Liberator covering their asses and drastically understating its actual capacities, or is it actually the case that one I could assemble out of a metal barrel and some bricks is four times as powerful?

Any insights here would be much appreciated!

I believe that Uncle Mud has gotten 20' from a liberator.
Maybe he'll see this and chime in with a more accurate answer.