in my TT, it is cutting off the 1040-x explanation at about 255 characters, I need probably 2x that amount, not seeing where/how I can get more? attach a statement? The IRS form seems to allow many 100's of characters.
The screen for the 1040-X explanation in the Step-by-Step interview allows you to enter 5 lines. Each line can contain up to 256 characters. If you switch to forms mode you can enter another 5 lines of 256 characters each. That should give you more than enough room for whatever you have to say.
you have to print preview your 1040-X Part III to be sure no text is truncated.
Even if e-Filing, I would not go out to 255 chars per line.
But, what do I know,
If you need more space enter "see more on attachment" and file on paper.
IRS says: for 1040-X, paper and e-File have the same processing time
AMendments are processed in the order received.
Refer to the Instructions for what is to be attached to Form 1040-X.
Do not include your old 1040 nor your revised 1040 because the Form 1040-X reflects any changes there and becomes your new tax return.