Stackable filament spool storage rack

There are a number of filament stowage solutions on Maker World, but none of them satisfy me: some go overboard with material savings and forgo strength. Some claim to print without support, but the quality is terrible.So I designed this, which has the following benefits:Material savings - only 130-140g filament per basic unitHigh strength - even when subjected to tens of kilograms of pressure, the units don't deform significantlyHigh expandability - can expand any number of units in any direction and freely choose to place them horizontally or verticallyEasy to put together - each unit is connected by mortise and tenon joints without the need for any toolsHigh quality - the main part of the storage unit does not require any support, not even bridges. This means you get perfect print quality on printers like the A1 I print them using Bambu PETG-HF, which makes about 6 units per kilogram of filament. I have made about 30 units and have not had a print failure.You can install optiona