TY4LOL wrote:

re-bending and re-forming the coil/legs to add another 1/2 turn will lengthen the total length of the twisted wire used

perhaps I phrasing it wrong
what will happen to a coil's resistance if I add 1 1/2 mm to the total length of wire used?

It will slightly raise the resistance because the length of wire being used in the coil will be longer