Evo is go - the results:</p>

12*7 APC prop at 7M - 83dBa - lots of pull, capable of accelerating a BH Extra (46 size) vertically upwards, but too noisy for our site</p>

13*8 AOPC at 7M - 78dBa - noticeably less thrust, but enough to fly with a limit to vertical climbs - 1 roll maximum before the speed really bled off.</p>

The first flight it deadsticked on a vertical downline after 4 minutes (6 oz tank), about a 1/4 of the tank used. It's still pretty rich on idle.</p>

Second flight drained the tank, every drop. Unfortunately I hadn't bothered to top it up after the first deadstick so another quiet landing.</p>

For the Horizon guys:</p>

On this side of the pond we have a national recommendation of 82dBa at 7metres, my club are a bit tighter at 80dBa.  On a 12*7 APC this engine is close, but just a shade too noisy, did you consider using a slightly larger volume can or maybe a slightly thicker wall to the casting to take the edge off the bark this engine makes?  Have you experimented with quieter units and if so what sort of results did you see?  
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