I custom built a similar system that Toucan does. I tested it to 2.5 Psi of back pressure at WOT 5650 RPM. The specs are max 2.9 Psi
I installed cone shaped ejector nozzles on the tail pipes so I can cut those back a bit more if I want to lessen the back pressure, but I don't think I will bother with that as it is within specs.
Toucan tested their system and state they are within specs but don't say what the results were, but I would assume it would be slightly less back pressure than the ones I made because they have shorter tail pipes and also a better baffle than what I could source. I just used perforated tube, and it is surprisingly as quiet as the original Rotax muffler.
I think the Toucan system would be a good choice and could also be adjusted to fit almost any aircraft; they are very well thought out.
