Here's some thoughts
So, 29 engines in 2016 and now 8 in the first month of 2017.
No use getting angry and imagining what we would do to them. We need to play to our strengths, share information, clues and intelligence AND get the forces of law and order to recognise and engage with the problem.
1) Do we really think that there was no "Recce" visit before someone waded in in the middle of the night and started removing engines ?. Failing that, Is there a common denominator somewhere in the form of a person within the community providing tip off's on security measures etc ?.
We should challenge strangers who appear at our airfields, note vehicle reg's, archive CCTV footage. The answers will be in there somewhere.
2) The most effective way to control the problem is to kill the demand. Registers of stolen serial no's are good - But the police will tell you that crooks have become so good at vehicle serial number fraud these days that neither they, nor the vehicle manufacturers can tell the difference. In actual fact lots of "ringers" only come to light from the vehicle electronics these days.
My suggestion would be to introduce an LAA / BMAA approved method of engraving the Aircraft reg on the top of the crankcase in a highly visible position. Yes, it could be ground off easily - but doing so would surely ring alarm bells to any prospective purchaser. If the reg is still there then there is always a trail back to the rightful owners. Similarly, smartwater / datatag are good - but not obvious enough to cause suspicion on their own.
Years ago I was at a motorcycle track day that was raided by the police. Turned out roughly 30% of the bikes had suspect vin numbers. At the time bike theft was rife, but the situation improved a lot when this sort of thing happened. We need to get this sort of Police support for our situation if we can. Random spot checks at fly in's ?.
3) We have more to offer the Police than we might realise. There have been several GA related people smuggling and drugs related convictions lately - surely the police need our support and vigilance here ?.