I'm doing one with the OS 91 and a tunnel does have to be made for the muffler I put it so the muffler goes down the bottom centerline of the fuse, I have used the OS 91 and and the Saito 100 in same planes with the same proformance but I'll see Monday, maybe earlier how it does I'm not much on 3D but I think it will be marginal with 16X4w apc.