I wrote a bit about the Mono saws in the chainsaw collectors' Swede-based forum:
********************************/phpbb3/viewtopic.php?p=209562#p209562We discussed the Mono saddle-tank saws there and the later SL-series Monos. There are a couple of brochures showing various Mono models. The SL-249 model is a big 7.5-cube saw. And there is a Mono saw with the little O&R model airplane engine.
The Mono saws are quite an interesting line out of Springfield, Missouri.