No bullshit from this fish!
I just placed an order for 8 sheets of the "magnetic paper" -- A4, 0.3mm thick -- for $8.
(not my photos)
I plan to use 4 sheets to print one geomorphic map.
A4 dimensions are 297 x 210mm.
Geomorphic maps are 430 x 280mm.
A quad arrangement of A4 (= A2) would then be 594 x 420.
If you printed right to the edges you could increase the dimensions of one map to 594 x 388mm, or roughly 40% larger if my late afternoon arithmetic is correct.
If I leave a comfortable 10mm border margin on each page that's still a nice 30% enlargement over the standard size.