There is now a video walkthrough of this level linked in the first post (and here), also recommended for those who don't plan to complete this map due to its difficulty (a lot more timing-based puzzles than in my later projects). I also have some speedruns of the first Standard Levelz on this YouTube channel. It's likely I'll record more gameplay videos over time, though I'm not sure which difficulty level should I set as the minimum if I were to record more walkthroughs of my own levels.
I have now captured the YouTube video and uploaded it to the Forum's web host ... 346,353,737 bytez(!) with a running time of 29:50. It is almost midnight, and I am too tired to update the Announcement with alternate links to the non-YouTube version. (The loss of several files that were on off-line storage (including YouTube) initiated a project to determine such off-line files and (try to) copy them to the (paid) Forum's web host ... no ADs.)
While capturing the video from YouTube, it occurred to me that the GunHat was no required. The Sword Grunt dispatched by cannon could have been dispatched by the SpongeGun a Grunt already had. Just shoot the enemy Grunt twice, onto the Spikez tile and let him expire there, leaving his Goo on the Spikez.
I think you are right. My original idea behind including the Gunhat might have been the long range required to hit the Bomb Grunt next to the fortress, but one can still reach him with the Spongegun, so it's not really required to pick up the tool to complete the level.