Dual top mounted spool holder

I designed this spool holder because I upgraded my printer for dual filament printing.
I love top mounted spool holders but they seem a little flimsy to hold two filament spools.
I need a Hard-Core spool holder for this...

It's designed for 52mm hole spools, the small spacer is for 750g spools (55mm max width) and the large is for 1kg spools (80mm max width).

Each spindle takes two 608Z skateboard bearings.
For the brackets you need 9-M4x10mm socket head cap screws, 9-M4 T-nuts or squar