Does a W1 fit on a 3535 mcpcb like the oslon black flat did or does it need a smaller pad
Just like the Black Flat.
It can help to check the board beforehand with the led, the pad dimensions of 3535 boards differ slightly with each board brand, some are a better match to the 3030 leds than others.
I wouldn’t really recommend it. It can be and has been done.
The CSLNM1.TG is 3mm x 3mm like the black flat.
The CULNM1.TG is 4040 and will not fit.