I’ve done this both ways a few times, and still bounce between Europe and the US a lot. Once I got used to A4 et al I found it maddening that the other sizes a

I’ve done this both ways a few times, and still bounce between Europe and the US a lot. Once I got used to A4 et al I found it maddening that the other sizes are missing in the US. A4 vs Letter is no big deal, IMO, with modern printer drivers and PDFs and so on. But once you start making regular use of A5 and A3, it’s hard to adjust to their absence. However, the DIN sizes are not the only standard sizes in Europe! There are also (de facto?) sizes for art paper, canvas board, and stretched canvas. For example, 30x40cm is a standard size for painters, and A3 (almost but not quite the same) is only really used for drawing… and sometimes for prints, depending on technology. On the US side, 9x12in is a standard size for both drawing and watercolor. And it fits exactly zero frames you can buy off the shelf in Europe. But at least 16x20in is almost 40x50cm! That’s been a lifesaver. Just today I was pleased to realize that my “weird” sized Chinese watercolor paper — Baohong, good stuff - is within a few mm of A5. Because I’ll take any standard at this point.