Meow's comment encourraged me to try this again. I was not able to even reach the exit be4, I just couldn't see how to do it, to not run out of blocks. Today I finally reached the exit, for the first time. Will try to find major cuts that I need, now. Very interesting level, indeed!
I finally beat it and am pretty damn sure the 404 is optimal, so well done sspenst.
Level is pretty fun imo but substantially harder than I intended it to be. Optimization here is really difficult and there are actually several 2 offs.
This level looks intimidating but it ended up not being that bad to find the general route to the exit. There are a lot of small cuts to get this down to 420 though. One of the 2-cuts is quite satisfying to figure out, was happy to spot it. Pretty fun level overall for me.
EDIT: I've had to edit this review so many times. Still don't know if this is optimized, getting a 400 would be really cool.