You have a rectangular silo; straight L- profiled ribbons need a heat resistant glue, the silicone stuff has no glueing properties + leaking rivets is no pleasure.
I have suggested some of the metal glues, that the American colleagues have presented. Sawing up the connecting foot a bit will take care of the differing heat “pumping” toward the steel silo.
Narrow sawed-up jumps in the foot and part of the “long L”-part at each 1" will allow enough “heat-play” longitudially.
Take your time and study the American Al-based glues; some of them withstands >500*Celsius!
The internal fan blown ribbons add nothing new for curious watchers!
Wood-framed “behive frames” vertically with 10 mm air-slots between them are well ventilated, but taking off the individual outer peripheral wood frames is a delicate job, each time you should clean them, is nothing pleasant in the long run!
The horizontal silo-ribbon cooling by the fan keeps all the condensate and tar where it belongs, without any extra undertakings, well hidden!
The cooling air-stream, split in two, one on each side of the silo makes for an even distribution and effective cooling.
For this you need tight cowlings following the cooling ribbons on each side of the silo.
Repeating the ribbon profile suggestion 3 X 15 mm, 1mm thick Al,
3 mm being the “foot” for glueing to the silo-sides. ~120m.
Tight, foot to foot… like on an air-cooled air plane motor.
The gap between the fins has eventually to be fitted to the pressure of the blower; avoiding too much friction for a weak blower.