Here's another thread with some useful information: /forums/726600/ShowPost.aspx.
Unfortunately Trumpeter's Mayflower kit is rather dubious in terms of scale accuracy! It appears to be mostly based on the Imai kit, but the upper works and in particular the masts + yards are out of scale (too small) with the lower hull. It retains the Imai kit's rather unconvincing flower + dolphin decorations on the stern.
Imai's Mayflower, BTW, appears to be based on a different set of plans than the Revell kit, which is based on the replica Mayflower II. Other than the aforementioned stern decorations, it's an excellent kit. It actually scales out at around 1/60, not the 1/70 given on the box, which would make the Trumpeter kit (if it's larger than the Imai one) closer to 1/50.
I'm guessing that Trumpeter decided to copy the Imai kit but added the upperworks from the Revell kit in an attempt to make it look more like the Mayflower II replica - but somewhere in the process of scanning/pantographing the scales got slightly mixed up, and they also forgot to scale up the masts and yards along with the rest of the ship.