I apologize for not getting to this sooner, but you are correct. The tiles aren't set up for RPGMaker. I tried it a few times with this tileset in the past, but I have so many tiles that they didn't fit the way I expected. I mostly used RPGMaker 2003/XP when I first started making pixel art, so the formats of VX, MV, & MZ are a bit less familiar to me. It was also taking time away from creating new tiles, but I totally understand the need so I may look into trying it again in the future.
Also, I'll look into adding underworld tiles to the overworld. I think it would be a great addition.
Hey, no problem and thanks for getting back to this.
I can make these work in just about any format, but I know a lot of folks are less comfortable with doing edits.
RPG Maker's newer iterations are pretty straightforward once you figure out where the engine slices the tileset sheets, except for those dang auto-tiles.
I've picked up every set you've published so far and plan on continuing as long as more stuff gets published. To echo a sentiment above, I'm in favor of smaller, more frequent releases that perhaps get updated as new stuff is ready - but it's your work and I am just an antsy game dev that wants to make awesome castles and stuff :)
Thanks for considering all of our feedback despite having a full-time job. I just emerged out of the busy season in my industry and it feels like I'm WAY behind on developing now - so, I empathize!