The MDS .40 most likely will not fit and will be way too heavy for the nose. The O.S. LA .46 isn't really a true .46, more like a beefy .36 the plane is rated for .25-.32 but I dropped a LA .46 into mine with no problem (well maybe I did have to spread the mount very little to pop it in. and I mean very little) and get this, I had to put the rx battery and the rx right on top of the battery (which I guess when it's right side up the battery is on top the rx and right behind the tank(basically where they show you to put it) because it was tail heavy, even with that LA .46.

The link setup was the hardest part in building this plane. Make sure you install the aileron servo with the output shaft toward the leading edge of the main wing(I put it in the wrong way and it would not clear the throttle servo) also use lock tite on those ez links connectors they use on the throttle and steering servo arms. They use a nut on the bottom instead of a locking collor(mine came off, story on that in a sec) I did have to bend the elevator push rod where it exits out the AFT end of the fuse, so it was more in line with the horn on the elevator. The rudder lines up better and doesn't really need as much bending.

The pictures suck as far as for the link setup in the manual and can confuse someone whose hasn't put together many planes yet, when it comes to setting up the links. When looking down at the fuse while it is upside down and nose toward you. The rear servo tray will have the elevator on your right with output shaft toward rear, cut all arms off except one (duh) and have it toward the wall, it's push rod will exit out the AFT right side and connect to the elevator horn (with bending, and some time trying to get it to exit out threw the cut out in the AFT section). The rudder/steering servo will be in the left tray with the output shaft toward the front of the fuse. The steering link will be the wall side and the rudder is the inner side of the arm. Push rod exits out the left AFT section of the fuse. The throttle servo is in the front tray with output shaft toward right side, remember the locktite if you use those ez connectors they give you.

I left mine as a stock sonic with the tri-cycle setup. Take off was fast and easy and was airborn with the OS LA .46 running a little rich to finish what little break in this engine needs. Just needed one touch of aileron right trim.

Did I tell you I got the sonic and OS LA .46 for $100.00 at the LHS

Anyway. I did some passes, then stall tested it, it doesn't tip stall (although maybe if the elevator travel is way up it will tip stall/snap). will pitch forward quick and go into a dive, with no power you may have to dive about 10-15 feet to build up flying speed again, throttle up and your pulling out of the stall no problem. Slow flight is stable, doesn't really rock on it's wing. Rolls look nice and slow, practice using down elevator and up elevator as it rolls to keep level flight. Inverted pass down the runway (did my first low one or I should say lower one maybe about 10 feet with it) upside down you have to start holding down elevator to keep the nose up (remember we are upside down right now) to keep it from diving too much. The inverted pass was sweet looking.

Landing is easy but you have to have a far approach if there is no wind to slow you down, remember it's a thin airfoil so it will keep up speed longer than a high wing trainer with a thicker airfoil. I bounced it once or twice and the gears handled it.

Now for the crash test. This wasn't good, I was practicing touch and goes and on one of them the engine didn't throttle up fully as this happen I was trying to blast off vertical because the .46 LA will pull it unlimited vertical (I did it a couple times) well that time it stall about 18 feet up and right in front of me. I stepped back as it stall and it swung toward me (it was trying to kill me I think) it pitched down and shot passed me and I knew it was going toward ground I pulled back at the last seconded to land on the prop breaking it off and get this, it bent the main nose gear almost all the way back but didn't rip the main gear mount off the firewall nor did it crack the firewall. It was all intact and would of flown again after replacing the prop but found that the throttle servo wasn't moving the throttle so I opened it up to find that the ez connector came off the servo arm and the nut that holds it on was inside the main wing because it feel threw the aileron servo tray because I didn't use locktite and this is also the first time I've seen threaded and a nut used, usually it's a snap keeper that holds them on. Once thats set it will fly again.

Other than using the OS LA .46 I say the sonic is a sweet forgiving flier in the stock setup and recommended control throws. The tank gives me about 10-12 Min's and is maybe a 6-8oz tank. I had a lot of fun with it at the field and look forward to flying it again. I started with the Alpha trainer then the Ultra stick 60 and say the sonic is easy to fly and makes a great low wing trainer, maybe even easier to fly then the ultra stick 60.

Hope this helps