Central Valley California
I would trade my #18 Ki-61 'Tony' for your #21 MS. 406 'Matimaha' but a one plane trade isn't really worth the postage or time it takes to box it up and go to the post office.
I look at it a bit differently -- I use a PO BOX so I go the post office three times a week regardless.
Under $3 shipping is better than ebay prices + high shipping in my opinion.
Would love that trade, so please do indeed let me know if you change your mind.