I believe that the MKVI is pretty similar to the MKV (my car). Does your seat bolt down with 4 large bolts that all go straight down? If yes, read on.
My problem is slightly different, my wife is "normal" in size. However, I am about 6'8" tall with a 37' inseam. I wanted to move MY (driver's) seat back a few inches. You need someone with metal fabricating tools and know-how (I do not know if that is you or not). Take a piece of steel stock about 1/4" thick and 1.25" -1.5" wide and cut it into 2 pieces each a few inches longer than the length of your seat mounts (front to back). Then drill 4 holes in each piece - 2 pairs of holes spaced exactly as far apart as your seat mount bolts. One set (pair) of holes will be the correct size for your stock seat bolts (rear ones countersunk? see note below). The second set (pair) of holes will be a few inches behind that first set (how far to you want to move the seat back?). This second set of holes should be sized to install heavy duty weld nuts from the bottom - someone's life depends on this seat mount.
Now you can unbolt your seat and bolt down your "adapters", then bolt your seat into those weld nuts. Presto, seat moved. Now, I don't even put my seat all the way back unless I'm on a long highway drive. Note: on my car I had to use countersunk 10mm bolts and countsink the bolt heads so that the seat didn't hit the bolt heads as the seat slid back. YMMV.
Have Fun!
Don