You should be measuring from the edge of the WHEEL to the edge of the frame and do the same on both sides and that would center your wheels correctly and give you the correct distance for the back of the wheel to the edge of the frame . This way would be much easier and more accurate but you do it like you wanna it still accomplishes the same Goal. Also may I ask WHY did you make the front end so WIDE ??????
Its like a 750watt 48volt. It has dual batteries which is cool. Assisted Speed without pedaling is limited to 20 miles an hour with peddling they say 25 to 30