What servos are you running? JR 537

Where did you put the battery pack? As per the instructions below the RX

Did you change the tail wheel? No, but the one that came with the kit looks OK.

Are you using the stock muffler? Yes.

Using a friends Great Plans CG tester (Top Tool) this was the story below:

In the end it took 15g's of lead on the front to get the CG right at 3" back from the leading edge and 9.1g's of lead at the opposite end of the muffler to get the lateral balance right.

Will let you all know how the maiden flight goes.