20mm it is, spoke to hope this morning and he says the same as you TJ,
im going to pop the wheel in my dh bike and see if it is the same in a proper bolt on rather than just the maxle.
ive since tried it in my other pikes and it does the same in those forks, still waiting to get my dh bike back.
so my question is if it is the maxle how do i go about making sure its tight enough it doe seem awfully tight ??