After playing Polish for about 6 months (in the US, using Matula, Dan Niel's site, and the book by Krystof Jassem) my partner and I decided to allow our 1D opening to include hands of 18-20 (or even 21) that were a) minor two suiters or b) long diamonds (possibly with a 4 card major). That's because Polish (at least our version) incorporates a 2D "Fit Reverse" (where 1C-1M;2D shows 18+ with 3+ card support). So now we'd have to jump to 3D. Heaven help us if the auction was contested. Stretching the 1D opening range wasn't a big deal, because responder tends to keep the auction alive with a 6 count to hunt for a major or 1N. In contrast with 1M where responder will often just pass with any weak hand. In theory having 1D be capped at 17 (or 18) meant we could do a lot of clever things with 1D-1H;2S or 2N, but those never came up, so we just removed the cap and play that opener's jump rebids (except 3D) showed a hand that didn't open 1C because the shape was wrong. We also decided to switch 2N from a preemptive "unusual" to a strong (we upped it a point, to take advantage of being able to get out in 1N with a 20 count, but that's a quibble). We did that because we got killed a few times (it's so much easier to interfere over 1C instead of 2N), but it ended up making our rebids after 1C much cleaner, especially in competition, because the balanced 2N opener wasn't a hand responder had to worry about. The reason for stretching our 1D (and, in a way, 2N) bid is to remove some of the burden from a nebulous 1C. So now our rebids are clearer. If you just allow 1M to be larger, then it doesn't clear up your rebid structure, just makes the point ranges different. If you allow you 1M range to be larger for "specific problem hands" that may be different, but we don't tend to have many problem hands that open 1M that can be solved by ranges-shifting. IMO.