about the only time you could have orientation issues would be straight on (when it's flying towards you, because you're pretty much using the LG as your orientation. Other than that, just put a contrasting scheme & you'll be ok.

As for the engine I'm not sure about those choices, but here's my setup.
OS 46 AX with muffler 17.2oz. Futaba 1000mah NiCD battery (4.2 oz.) shoved all the way against the FW under the tank. I still had to add 1 oz. of nose weight to get it to balance.

I believe the YS weighs around 17.9 oz. so it will be just fine from a weight perspective.

Here's an early video of mine to give you orientation perspective. I don't have wheelpants on, so it makes a little difference straight on.
http://www.uwood.net/video/rc/SSE1.wmv only the third flight, so I wasn't wringing it out yet. ;-)