RE: GP YardStick Help (Research B4 U Buy)
If you look at the tens of thousands of products Tower Hobbies handles, you can understand that not every "order taker" is going to be familiar with every plane and every bit of electronic equipment, or whether or not what you ordered will be compatible with everything else. They just answer the phones, and probably don't really know much about R/C beyond what they pick up through taking order after order all day. You bought a plane and a radio, which is everything you need for A plane, just not necessarily YOUR plane.
That said, you didn't do too bad. With a little creativity, the HS81s can be used on the Yard Stick. From the looks of things, you've got the creative gene? I can't tell if the servos are mounted or not.
Don't bother with the Slow Stick. You've got a YS, so why spend more money? We can fix your plane, and you'll learn a lot in the process. There's nothing about the YS's design that makes it a bad plane. It's a great design, well built. You just need to do a little tweaking now that you have it. Nothing unusual about that; it's what this hobby is all about!
What specific issues are you having with the plane? Describe them, and we can work them out.
Your main problem will be with the motor. IIRC, they stick you with a wimpy Speed 280 and recommend a 6-cell pack. There are two ways we can go with this. Either switch to an 8-cell pack, or swap out the motor for a "hotter" Speed 300 that will draw more power from the batteries and put more into the prop.