devens,
I'm using the HS7955 on the Rudder, elevators and ailerons. There is no reason to go more than that. In fact I'm sure the 7985 would be fine on everything but the Rudder, but I think you only save about $10 a servo. For me it wasn't worth it so I went with all 7955, They are nice servos.
I just purchase a DLE55 to put in an Edge that I'm working on. I haven't run it yet...but it weighs 3lbs 4ozs with the sparkplug, the ignition, and the stand offs. That is the exact same weight as my DA50R. Exactly. And I'm hoping, because it's 55cc it will be a little more powerful than the DA. Hoping for 2 extra pounds of thrust, but I'm not sure. In a couple weeks I can tell you if it meets my expectations.
Probably the lightest and best engine for the Yak is the BME Xtreme 58CC. This mutha is a POWERHOUSE. I'm getting about 29.5lbs thrust at my elevation, turning a Vess 23-B prop at almost 7100 RPM. My (3) DA50Rs give me about 22.5lbs thrust. (these are realistic numbers, though many will tell you they get more, but I'm at 4800' elevation) It weighs 2lbs 15.5ozs with the ignition and sparkplug and the shorter standoffs. It's an amazing engine but I can't yet recommend it. I bought two engines and have exchanged them back and forth (sending the other in for repair). They have netted me a total of 18 total flights. I will say that Tom has been very helpful and knows he has had some problems with the engine and is gladly warranting them doing the required upgrades at no charge. This most recent engine for me (the one I just received and mounted to my Yak and flew the 3 flights yesterday) sounds different and more better. It runs great right now. I don't have more than a 5 flight sequence yet. But I'm willing to bet this one will be much better. It just sounds different/better. I noticed serval changes that look like improvements. If the engine lasts (I also have a friend in Ashton that has the same engine but his failed also) then I'm gonna say it's the best selection. But, I not sure you want to take the risk or not. Power is ever so important to me because of the losses in our thin air. This plane wih the BME, when it runs, is about the best power to weight ration I've gotten. It is impressive. Here's hoping it lasts this time.
I'd make sure you mount an optical kill switch similar to Smart Fly. That is a feather weight option that really gives me piece of mind and is a lot safer if something goes wrong.
I can wholey recommend the A123 Batteries. I changed over to them just this year and I love them. I now have 3 planes (55CC Edge will be 4) that I'm using them in. I conserveatively get 3-4 flights before I must recharge. It only takes 7-10 minutes to charge in the field. They are great and very high performance. Tom at Wild Hare is the best place to get them I think. He has a starter kit that includes a battery, a HD switch and a A123 charger that gives you the input mA when you charge. It's a great combo, $129 I think. And he's a good guy to get stuff from.
I wouldn't go with foam wheels. They really tend to flat spot. Especially with a plane this heavy. I used DuBro 4" tires, rubber. I think they weigh 3.5ozs each. The foam would save 2-3 ozs but I don't like that flat spor issue. I use them on my glow planes that weight about 7-9lbs. But this is simly to heavy.
If you use the BME engine it has a side mount carb and I just drilled a 5/8" hole in the lower right side of the cowl and reach in about 1.5" and turn the choke on/off with my finger. Saves the choke servo set up (especially hard with the BME because of odd angle of carb) and the 3ozs weight of the servo/arm and lead. You could drive a very small hole and use a small screwdriver if you wanted but the 5/8" hole doesn't distract and kinda looks "trick". If you use the DA or DLE you can make a primitive wire manual operating lever to activate the choke.
You'll probably be very satisfied with this airplane. Most are.
Good luck.
thanks
Barry