Well, this is my modified (both from original Tatoo's design and from the first time I built) SPA3D.

The first time, I made the engine mount out of wood. ANd it nly gave me headaches[][]

The first 3 flights, well they weren't flights at all, the plane cartwheeled right after takeoff (first due to too much sidethrust, then due to a sudden gust of wind, and after that due to an offcenter rudder) ripping the enigne mount all these times. On the 4th time, I forgot to screw the enginemount in, I only glued it and when I applied full power to star the takeoff roll....yeah you guessed right....the engine jumped forward, ripping the mount again.

I also made a new landing gear out of 5/32" wire (the old one was too short) and a new tail skid out of 1/8" wire (the old, out of 5/54" was too flexible). I found out I am able to steer the aircraft succesfully on grass field only with the propblast acting on the rudder, so I think a tailwhell is unnecessary hassle. Now I made a decent mount of poly.....I won't be able to test fly it today, but I will see for tomorrow. Flight report will come ASAP.

Here's a little specs:
Wingspan: 30in
Length: 42in
AUW: 1750 grams -> 3.85lbs
Enigne: Enya SS40BB
Prop: MA 10x6

I also found out that it's a little off balance lateraly. I am thinking of puting nails on the flutes of the opossite side to balance it....Is it OK??

Here's a pic of it with the old mount:

Here's a detail of the throttle linkage. I used a ball link in the servo arm and a nylon clevis at the throttle arm and an 1/8" plastic tubing, so that when the engine mount gets ripped in a crash, the servo doesn't suffers damage. At least it has worked so far.

Here's it in the actual stage:

A detail of the tail skid installation

And here's a detail of the underside showing the foam board I used onside the LE to give it stiffness. It is very stiff, I ground tested it to 2kg (about 4lbs) on each wing tip and it flexed very little. I have also put 2 3/32" wires 2 and 4 flutes away form the aileron hinge line.

These planes seem to be more sensitive to lateral balance than front to back. Make sure you are balanced before you try it again. I had the same problems as you on my first SPA3D (side thrust and lateral balance). On both if my spads the amount of weight needed was appx 1.5oz on the wing tip. To balance your plane, try this. Make a base (I use a 2x4 nailed to a peice of 12x12x1 board) then drill a hole through the peice of 2x4 the size of a pencil. Insert the pencil eraser side up. Now, mark the channell 6" back fron the LE of the wing and set it on the eraser and balance. When you have it balanced it will sit perfectly on the eraser. It also looks cool to display your plane this way.

Keep working at it and you will be rewarded with many hours of enjoyment

William