Replace all tubing and there should be no bubbles anymore. Those no-bubble clunks are nice and may prevent some of the bubbling, however it's what we dutch call 'fighting the symptoms rather than the problem'. The fuel shouldn't foam, period. Lots of people are flying with this engine, or similar ones, without having these problems.
[edit]better put: an OS 46 AX on a roughly 80oz (5lbs, 2.2kg) plane with a wingspan of about 65" (1660mm) shouldn't cause so much vibrations that the fuel foames[/edit]

Did you balance your prop?

A header tank (hopper?) like used in some helicopters may possible solve the problem as well, but makes your setup more complex and it shouldn't be needed.

My guess is that there is a small puncture in a tube somewhere, leaking air into the fuel. That or maybe your prop is not balanced (or somehow got unbalanced) and this causes extreme vibrations (which will also ruin the bearings).

As far as hooking the whole thing up; you might want to consider a uniflow setup, though again that shouldn't be neccesary. The advantage is that you'll get the same amount of fuel all through the tank, as oppose to your engine running leaner as the tank empties.

http://www.fraserker.com/heli/uniflo...flow_works.htm

I'm not using foam around my fuel tanks and so far have had no problems with it. My closest setup was an OS .46 FXi, which ran fine with a normal clunk in a normal (dubro) fuel tank. All ARF's i have owned so far (5) had a tank installation in such a way that you simply couldn't put foam around it.

I do like to use filter clunks, at least, if we're talking about the same thing


Filter clunks are supposed to filter. If you want it to do that, you shouldn't fill your tank through one, since that will put debris/sand/whatever from your fuelcan into the inside of your filter, meaning that it would be the first thing to go to your engine. Another reason might be that the filter loosens or might even be washed off when refueling.

However, I used two filterclunks, one in my fuelcan and one in the tank. and use a fuel-filler valve between tank and engine to fill the tank. Periodically I check both the tank as the filter, and so far i have seen no problems. This has lasted for about 300 flights now, without any problems.