ORIGINAL: Jezmo
I am not sure how they handle MDS's in the UK but the ones delivered to the US are set up for 10 to 15% nitro. (Someone told me about running low nitro in mine because of it being an eastern bloc engine and when I tried it many problems came up so I went back to 10% and all was well again. Later I was told the US bound engines are set up different because of the fuels we tend to run.) It doesn't like little props (It's not a screamer) and I run an APC 11X7 on mine but it will also turn a 12X4 or 5 pretty good. The most important point of my ramble is mine would not run well on any plug other than an OS A3 and on that plug it runs very good. Good luck with yours.
Edited to add: Like Dar says they like Castor in the fuel. I run Omega in mine which is 70/30 blend synth to castor. Also, mine had a lot of pinch when new and took a gallon or so to loosen up and that's when it really started to run sweet. It still has a lot of pinch but not like when it was new when I had to use a hair dryer for the first couple of tanks to start it.
I have never seen or heard of any MDS set with different factory compression ratio for the US market. Possibly, if they had, they might still be in the US market? You might want to verify the source of that information. Sounds more like a WAG or wishfull thinking than fact. I have personally run the 1.48, .48, (2) .40s, and none of them was special anything for the US market. They are fine engines on their own merit. Like my others, the 2 .40s I have today run best on 5% nitro fuel containing at least some castor oil (Omega).