Hello! I love the mod and made some modifications for myself that could maybe be considered to be implemented.

I changed the item's and recipe's subcategory to "storage" so that the "belt" subcategory does not extend to a new line, saving some space in the window.
https://i.imgur.com/pKxnHM0.jpg
Also i made some more accurate sprites. I don't know if you wished not to use them specifically for some reason, but if you like'em feel free to use'em!
zip of the icons folder:
https://drive.google.com/open?id=1cuXCT2BvA5AoqbE0NhD71IRS2j8t07yY

Lastly, does this mod add gourds to the game? i think i saw one spawn but it might've been my mind playing tricks on me...

PS: is there a way to limit the PGO to only be crafted manually?

This graphic is as it is because I didn't want to use any proprietary graphic from the Internet for legal reasons. So I made this one by changing colors of solid fuel.
I made it also half-transparent but this was for game-play reason. I want it to be inconspicuous, not very visible. The whole point is that this item is placeholder that fills dead ends of belts and so on. It shouldn't be noticed by the players until they are actively looking for it. So I'm not going to use anything that doesn't fulfill that criteria.

I draw some of my graphic in MS Paint and I agree that I have no graphic talent. Yours certainly looks better. I could consider using it but I need to know if you made them yourself. If they are legal, feel free to make a pull request on github.

About the gourd: I am entirely sure that in my mod there in no vegetables and there will never be any.
However, if it was here, it chance to spawn would be exactly 0.
You've probably experienced some weird bug. My code may be a little volatile due to the fact that it is difficult to made a recipe that has no product.

"PS: is there a way to limit the PGO to only be crafted manually?"
At this moment no. Is there any reason for this.

yeah, i guessed those were possible reasons for the current look of the sprites. good job then! they work perfectly for what they need to do. : )

and eh, no. I stole images from the internet and then edited them a little. I doubt you could just put them in the mod like that. : \

but yeah sorry about the gourd thing, i must have confused this mod with another!! my bad.

About manual crafting only...
I don't know how, but what if the possibility of having infinite items for free was used to grief? I guess it's very unlikely this situation would happen... but imagine somebody replaced ore with PGOs in a mining outpost far from other players' sight. The main unload at the base would eventually receive a trainload of PGOs and it would mess the system or some shit.

again, this would be very unlikely but you never know! Dealing with infinity can be dangerous! D: Maybe i'm just overthinking it so don't worry. thanks for this mod by the way! \o/

During a quick research I found out that you can only block hand-crafting of an item. Perhaps, there is some way to bypass that like using a side effect of some other property. I might look at this some more in the future.

"What gourd"?