Again, I am not like great or anything at the Mario's. I've rarely ever have played hacks and such, and any ability I have, is from the actual games. So I can understand if you want to disregard a lot of my points. The level isn't really made for someone like me, but I'm glad you still were able to take some of what I said to heart.
I will say though, some areas where you aren't supposed to jump don't always feel right. It's scary to take such risks, even if I, as the player, think that might be the solution. I've died and have had to restart enough times where I'm not ready for that type of thing (again though, this is from a less experienced player, and might not apply to those who get to this point in the game).
I am sorry I didn't catch onto the running thing though, sincerely. Be careful though, if a section is too finely tuned to work exactly one way, it needs to work well that way. It's easy to disregard intended methods at times, especially if the intended method doesn't work the same every time. I know in some areas I was trying quick low jumps, but I'd get the wrong speed, and that would make me not want to try the correct method as much anymore.
Coin paths could maybe work, and in some situations could be nice indicators (maybe like a coin every now and again on the run areas to indicate when you should be staying low, and upper coins to indicate when to go high. Doesn't even have to be trails, just single coins that you can try to aim for. I don't know if that would work, and maybe isn't the best way, but maybe a consideration).
Taking the columns out isn't totally necessary everywhere. The ones near the end, though foreboding for someone like me, seemed like they would probably be fine? I just didn't like the ones early on I supposed.
Agreed on the bullet jump. Neat idea, but without a more consistent source of bats, the bullet is too irregular. For a precise level like this, you don't want to usually leave things up to chance. Would it be possible to put the bats in that area on a generator perhaps, so you have a supply of them to stay on for awhile while you get the timing?
As for the shortcut, seems a bit backwards. You're worried about length, but you include a shortcut that skips most of the first area? It's a nice reward... but invalidates that bit ahead of it. In the very least, the clue to it should maybe considered at a farther point? I'd personally make it so the shortcut skips the first part, and takes you to half way through first area (again, cause I was bad at that first bit though). Even ignoring my skill though, seems weird that someone willing to take the risk can just skip over half of the content of the first area without ever seeing it.
I suppose length is different each player... however it sounds like Sedron and I both took quite some time to beat your level. WestonSmith took 15 minutes, and I took nearly an hour for what I got through. That gives you an idea of the range that a player can take to find that right momentum and thinking to get used to your level and beat it. Again, I don't have a ton of experience playing levels, but I've watched raocow play a lot of stuff, and I'll peek at peoples thoughts on stuff. Length is a difficult mistress to court, is one of the big things I'll see. Though at times, people will think a level needs just a little more time to fully realize itself, that just a bit more would be nice... I've seen far more complaints about levels that go on too long. Levels that over stay their welcomes, and get frustrating to redo. So get more testing to make sure your level isn't too long as it is. If you're trying to lengthen a section to match the other, in my opinion that's a dangerous idea (unless the padding is used as a way to give more safe-practice I suppose). I would say instead you should shorten the other area.
As for LunaDLL, sorry about that too. I'm using some older version before all that was fully implemented.