[secant0give]

they look like a nice servo george .
i'm using these ones , had to convert the servo cutouts to smaller , but they are light , precise , fast , and strong enough . i , hope it is for the push pull rudder setup up anyhow .
http://www.ebay.com.au/itm/NEW-Hitec-HS-...ccessories&hash=item1e6956b6cd

what motor and battery , esc , and prop are you using , and how much does it weigh ?
is that a HK katana ? are you happy with it ?

You won't have any troubles with the HS 5085's using them for pull pull rudder on a 50 size model. Rule of thumb I use is roughly 1.5-2 times the weight of the model in torqur (Kg/cm) for 3D/sport flying areobatic flying. I use HS5085s in my Edge 540 for all surfaces including rudder and it uses a pull pull set up like the the MX. No problems doing Knife edge with that one and it doesn't hover too badly either. My Edge540 weighs 2.5Kg I'm a little envious of the 200g lighter airframe. That's nearly 10%

I think for flying 3D and for sports areobatics, but to a lesser extent, weight is the enemy. It makes a plane harder to fly. Every bit you can keep off is going to help!! More wieght means slower acceleration and more stress on the airframe when it changes direction sudenly.

I don't think the cardboard tubes/sleeves are any bother, they don't have to add any strength, all the strength comes from the carbon tube that fits snugly inside them. The cardboard sleeves are nice and light, mine have shown no signs of wear yet and that Edge540 is nearly 3 years old now. It's had a quite a few flights, lets face it the sleeves are realy only there to guide the carbon tube throught the fuse pannels and wing ribs. If you want to toughen things up you can allways paint the out side of the sleve with West systems laminating epoxy. On a similar note, I usually paint the area surounding where the landing gear mounts to the bottom of the fuse with west's epoxy and add a little glass or carbon fibre in stratigecly placed around that area. I mainly do this 'cause our field can sometimes be a little rough. Tho' of late it's been excellent!!