Your extra should work ok for pattern, I have been experimenting with a 66 inch extra 300 s 4.7 kilo (10.4 Pound) with OS 160 FX 18x10 prop. It flys the expert shedule very well, loads of power, half throttle on the straight and level, 3/4 to full throttle for the up lines and ease the power off past the top of the loops and ease it on again begining on the last 1/4 so that you are back to your original throttle setting at the end of the manouver.the only trouble with the scale planes is little wobbles after rudder applications such as piont rolls or line corrections because they are so short in length. You have to be very very smooth with rudder application and release. A proper pattern model is easier to fly and is less likely to exhibit roll or pitch coupling. It is great to see a scale model at a pattern event for a change I think.