If you can sideways maybe the best, The engine will not load up fuel at low speed ( diesel seem more prone to this). It makes a neat installation, done with the with pitts type, mufflers, regardless of a regular muffler or pitts type the muffler is under the plane, looks good on on a round cowl, plane stays cleaner no residue on side of plane. I have even done this on trainers you do not have the big cylinder in front of the windscreen , sure you have to slice the cowl but gets it away frome the typical trainer look too
martin