3W includes a little information on baffling in the manuals for their in-lines. Also, DA's 100 in-line engine has been out for several months, but for some reason they're aren't advertising it. It costs about $500 less than the 3W.
http://www.3w-modellmotoren.com/file...R2_englneu.pdf
Photos on in-line installation are about half way down the page on this link:
http://www.3w-modellmotoren.com/navi...-pictures.html