Milton,
I ended up building an arch out of a 275 gallon oil drum. Honestly, it worked fantastic and took the 2'x4' mason divided pan to it's max capabilities (13 gallons per hour) for evaporation. Even with 2"x4" reinforced rails, I was able to get things glowing red hot with brick inside and those rails would warp all kinds of funny shapes and then slowly reract as things cooled. This of course was with a blower using mostly popple split down to wrist size and firing every 8-9 minutes, can't remember which now. I would trickle in slowly using a valve on the Mason preheater pan that yes, did drip some sweat back into the divided pan. I was able to get boil to reach all the way back almost to the inlet of fresh sap. Having the arch design I did allowed a lot of heat to come off the upper rear and push heat into the preheater pan which I think did help substantially from the cold sap coming in.

Conclusion? I think it would have been just as easy, actually easier, had I bought angle iron and went with a conventional design looking back. Of course looking back I would have started the endeavor long before 2 weeks before tapping I don't have pictures on my computer but I'll edit this post and load some from my phone!