Hi
Not too long ago I sold a 35 Global I had totally rebuilt, got my money back out, and now have purchased a CB40 Mosler from a man in Montreal who had been running it on a Hummel Cruiser, upon selling the Hummel Cruiser, the buyer wanted to try a HKS so he did not buy the Mosler.  The owner had run the Mosler through a speed shop of some kind and one of the things they ended up doing, much to the delight of the seller, was to get rid of the Zenith carb and go to an Aero Aarb.  The man said the result was an incredible transformation, in power, sound, performance, and responsiveness.  Supposedly the man has had eighteen planes, now has a Kitten in barnstormers, and I have seen him selling other stuff as  well, so he does have some credibility.  I went up to the Canadian border and met him and got the engine and have just now hoisted it up to begin getting the Max set up for it rather than the set up I had for the Global.  I never expected it would be a four point match to the Global, and it isn't.  I am going to keep the mount it came with and merely add some cross members to use the four hard points on the Max.  Overall, it is not that challenging, or so I think right now.  First question is one I think I brought up when fitting the Max for the Global, where is the thrust line for flat top Max, I think the discussion led to the consensus that as long as the thrust line lf the engine was close to the upper longeron, you probably were ok. Does that sound right?  I can't recall seeing it in the plans although it might be there.  There were a couple of other points I found interesting and only time will tell how they work out.  I asked him about oil cooling and he indicated he never found it necessary in his hundred hours of use, and also, the small steel plate that seems to always accompany half vw types, which acts as a crank counterweight I believe, was not there, and he indicated that the speed shop had balanced everything so well it was not necessary.  I can see that point bringing about an argument but my read of the man was that he was shooting straight.  Hummel did one for me on the Global, I had a Hummel engine that had it, and I just sold a Pup with 35 Mosler which had it, sure seems like they are a common item, again, time will tell I suppose, but I will initially run it without that little prop hub plate.  
All comments, thoughts, opinions, experiences, appreciated.  
Thank you
Kim Brown
New Hampshire

Thrust line isn't too critical. Ideally, aim for top longeron as you said.

Normally I would say that an absolutely horizontal to the longerons thrust line is relatively insensitive to the height of the thrust line.  More important would be the angle, both in the vertical plane and the horizontal plane.  I would certainly want to start out with a thrust line horizontal to the longerons and congruent with the longitudinal axis.  However it is worthwhile knowing that sometimes experimentation with a slight downward thrust line may actually increase performance.  I doubt that would be worth trying on an aircraft that has been around awhile like these, as angle of attack of the wing has probably been refined, but sometimes it has worked out.  On the other hand it isn't uncommon to find that a slight angle in the horizontal will result in an aircraft which "flies straighter" without constantly pressing on one rudder peddle or using excessive rudder trim.  This can slightly reduce overall drag.  These would be minor points, but it is worth mentioning.

Tom