RE: YS Engines
I have to agree with both posts.
The Focus Sport would probably be a better choice than the Leo 110. The Focus can be had either ARC or ARF for less than $300 so it isn't much more than the Leo and there is the build thread here on RCU so you can get any setup questions answered.
As for the Spot On 50; the ys 63 should be a great match.