US 86x86 "electrical box" to EU 60mm box converter

I live in the EU, and the wall electrical boxes here are 60mm and round.

(65mm outside, 60mm is hole-spacing standard) 
 

On AliExpress, I found some nice (and very cheap, 2-3$?) floor (stair) lights, but they're designed for American/British square boxes with the standard 86x86mm size (here's the link https://pl.aliexpress.com/item/1005007258429832.html ). 

Unfortunately, 86mm boxes aren't available here. Even if they were, they might be suitable for plaster or plywood walls, but installing them in a brick wall is a nightmare.

Because I like them and don't want to cut square holes in the brick wall (I already have round 65mm ones), I decided to make a converter. By moving the light fixture 10mm away from the wall and moving it slightly downward, I can fit the back of the light into a round box.
 

The adapter is screwed onto a standard round box with two or three screws. The holes are widened to compensate for a misaligned (rotated) box in the wall, ensuring the top frame is perfectly horizontal.

You can place four M3 heatinserts (4.5mm, up to 5mm deep) in the corners, or screw light with two main screws in the middle.

the back of the lamp fits into the round hole as you can see.

I printed my adapters from PLA because Pla paint very well with regular wall paint. 

In STL/STEP files are versions with different thicknesses (heights); perhaps they'll be useful for other US 86x86 accessories?