There are also a couple other options for Ikea racks other than the Pax, my large rack, currently has all my females is an ikea PAX rack where I can use either the 1m or 50cm Ikea complement boxes(for the pax system). I routed out slots on the shelves and use heat cable with aluminum tape over the top
Then my male rack is made from the 60x50x128cm stuva korpus, also using the 50cm complement boxes. It also has nice holes in the bottom where the feet would screw in, which happened to be the correct thread and diameter for castors i bought at the hardware store. This rack is headed with a heat mat per shelf.
The hatchling/baby rack I have is from the Ikea Trofast system. Its meant for children's toys. This rack is not complete, but it will have a trofast shelf siliconed above the sliders where the trofast bins fit in. Heating will either be heat cable on the shelves or back heat with two large heat mats.
Picture shows three racks left to right.
With the variety of sizes all these come in, there are a lot of options with the Ikea furniture, just got to get creative, like the OP did, looks great!
I will be finishing the baby rack soon and then building a hatchling rack with shoebox size bins, or likely anyway, when I get around to it I will make writeups. I also wanted to add that if you check the fundgrube, no idea what that is in english, but Im sure Ikea in the states has it, its where they outsell stuff or put all the damaged items. You can often find Pax pieces for REAL cheap, I think I paid 3 euros per shelf and something like 8 euros for each side piece. Worth looking, I just kept checking back everytime I was in Ikea (I live like 5min away so it was quite often) and everytime they had new shelves I bought more. I would say check craigslist or ebay or any local sales sites you have for used ones. New pax systems are quite expensive.