I had one and flew it with both an OS .46AX and an Evo .46. Both needed a brass, heavy hub to balance correctly. Both of these engines are heavier than the OS .40LA so you may have a problem. Adding weight to balance, especially nose weight, will further lower your performance. One thing you can consider, although it is a little trouble, is to move the rudder servo up to the radio compartment under the wing and use pull-pull cables. This would take a good bit of weight off the tail and may let you balance. I was doing a kit review and had to use the stock positions, and the more powerful ball bearing .46s handled the extra weight OK.

You really want to keep a fun fly/3D plane as light as possible for best performance.
1. My usual method for building these type ARFs is to build the plane without the radio, installing the engine, muffler and throttle servo.
2.Then I put the battery in a convenient forward location before balancing. This is so I can move it rearward for better flight performance later.
3. I then rubberband the elevator and rudder specified servos in their locations and check the balance.
4. If I am out of balance, I move 1 or the other, or both, to the rear or forward, depending on where the plan location was.

For the Twist, moving the rudder servo into the radio compartment would be fairly easy. You save the weight of the servo in the tail, plus the pushrod.

Another choice would be to use a lighter servo and check. Hitech 225MG servos come to mind. I like the Hitech 5245 mini-digitals. Both of these servos weigh 1 oz. compared to 1.7-2 oz for standard servos. Two ounces off the tail might do it.