I am a newbie to the sport of RC flying. I have been flying an AeroScout for a couple of months now and am able to fly it well, take off and land decently. Then I bought a Carbon Cub. OMG! I can't get it off the ground in any reasonable semblance of a takeoff! I switched to the landing gear modification using the Valiant gear. That didn't help much. I start to slowly increase the throttle and when it starts to go to the left I add a bit of right rudder. This works for a second or two and then it turns sharply to the left. This happens in a split second and there is no time to react. I have been told the wheels are toed in, then that they are toed out, then that they are not both in line, then the tail wheel is not straight. I had one of the really good fliers that flies jets fly my cub and he managed to get it in the air, but the takeoff wasn't pretty by any stretch of the imagination. Okay, so I figured out something to insure that the wheels were both in line with no toe in or out and strong enough to prevent any bending. What I did was use a 1/8" diameter rod for a common axle for both wheels. It goes through two holes in the Valiant landing gear mod. In between the two legs of the Valiant landing gear the 1/8" rod goes through a 1/8" diameter hole in a carbon arrow shaft. This provides rigidity for the axle and prevents the aluminum arms of the Valiant gear from bending. Then I bought 3" wheels to replace those huge wheels that come on the Carbon Cub. You can't use this if you fly on grass, but it should work fine on pavement. I tried it out today and it is rigid and keeps the wheels in line, but the plane still does that sudden whoop-d-do with no warning! I stood directly behind the plane on takeoff and could not see any advance warning of that sudden 180 degree turn! It is downright scary and a bit dangerous!
CAN ANYONE HELP ME? I AM AT MY WITS END!!

I would suggest a picture of the front of the airplane from the top and also information as to what brand transmitter you are using.

My transmitter is a Spektrum DXs. A photo won't help as i have changed landing gear yet again. If this doesn't work, I will then take a photo from the top.

The reason why I asked for the photo is I wanted to see the amount of right thrust the motor has, more specifically, does it have enough. Having the correct amount of right thrust coupled with a throttle curve ( a feature of your transmitter ) to smoothen out the power output would really help with the issue you are describing. When the airplane veers left, is it immediately following a big power increase? Your wheels, as long as they appear to be visually straight and one isn’t binding have virtually nothing to do with your issue.

After a bit of research, I found that your TX does not have a throttle curve feature while in airplane mode. So it may end up that right thrust optimized is the best that can be done. In the meantime, I suggest you carefully run up the motor from zero to full power while moving the throttle stick fairly slowly and see if at any point the throttle makes a big jump in RPM that is disproportionate to other throttle increases.