Well decision made and Suzuki DF20 ordered for delivery in around two weeks. During my shall I/shan't I thoughts Suzuki UK went out of stock of this engine with the potential of a mid April or early May delivery but the local dealer has managed to get them to divert one from the EU main depot to UK so I don't have to wait.
I did have the option of buying mail order from a south coast dealer saving £90 and it was in stock ready PDI'd. However my local dealer have put some effort into this deal and I personally I think my relationship with them over routine servicing and any warranty issues will be better than had I bought elsewhere.
It's going to be fitted with an 11" pitch prop and depending on how that goes I'll buy a second 11" or 10" as a spare... never go on holiday without a spare prop.
Jeff that Russian (FOREVA) guy's Youtubes of their trials comparing outboards and props are excellent. I was most interested in his trials using rev counter and GPS with a DF15 testing 10" & 11" props and comparing each pitch with 1,2,3 & 4 folks. Here is an example...
An approx summary of their WOT max speed results is...
1 person 19.5kts 5800rpm
2 person 19.0kts 5800rpm
3 person 17.5kts 5500rpm
4 person 16.5kts 5400rpm
1 person 20.5kts 5600rpm
2 person 19.0kts 5500rpm
3 person 17.0kts 5200rpm
4 person 16.0kts 5100rpm
Given the extra power of the 20 over the 15 in those tests I can see why Chipko is hitting the rev limiter 2-up with his Aerotec/DF20 combo running a 10" prop.
Thanks all for the chat in this thread and the various PMs that have helped me make a decision.