well the prisma's did it and had some issues. they did 4 not 3 heat sinks.
but a prisma pulled 1400 watts.
a triangle setup with 3 s-5 panels = 900 watts maybe 1100 if you push to freq 412.
two fans push pull with external controller I guess it could be done.
I thought the Prisma problems were more related to firmware, the exposed capcitors and breakable stuff and no thermal monitoring/shutdown of the chips? In the right environment, some people had no trouble with them. The Tube was a fantastic design/form factor. It took the hashpower, power rating and efficiency of an S2, and crammed it into a very effective and dense package. The fact that the BE200 chips were tough very thermally "tough" probably helped, those things get freaking hot.
Anyways, I think 3 hashboards could work with the right amount of airflow, it's about the same wattage as a Tube.