My recent contest levels aren't difficult. The reason they aren't difficult is because I was unable to patch the backroutes.
The intended solution on R3 is probably the hardest I've ever created, but I haven't been able to come up with a way to enforce it over easier solutions.
The R1 level also has an intended trick, and while several people have submitted replays with various skill saves, I haven't seen the core trick in any of them (the level name actually has some meaning to it) (although, disclaimer, after I gave up on it I stopped checking the incoming replays, so it's not impossible that someone might have gotten it since then).
I've basically given up on patching these. R3 wasn't something I could easily fix, and it received a little positive attention, so I just decided to initially focus on dealing with the R1 level. But on that one, it seemed like every time I'd release an update, I'd get 3 different backroutes, attempt to patch them, and the patch would completely fail to remove even a single one, because the original backrouter would always find a slight modification that made it work again. I'd at least want to get new backroutes and not just the same ones again.

The backroutes make these levels
significantly easier than was intended in the initial design.
Personally, I think if I were ever to create a full pack, I'd probably have to have someone help me with the backroute patching (not just the testing, but the patching too), because I'm not very good at it. Otherwise, it'd be full of mediocre easy levels, while I'd want the pack as a whole to have something to offer both new and experienced players. But if I can't remove the backroutes from the harder levels, then the pack won't really have anything to offer experienced players.