Cash-flow is king when you're building your own flying machine, and I am mocking up the motors for the 'look and feel' of the final product and for ideas on how to mount the real thing, as and when. You can do no better for this than floral foam, and here I have separated one of the polyurethane foam inserts from its plastic well, which can be upended and glued to the top of an intact unit to produce a double-sided cylinder of broadly the same dimensions as the T-motor U15 units set eventually to take their place. This costs around £4 instead of the £600 that would be needed for the original. If you want to try this yourself, use rubber solution glue because the solvent in most glues will simply dissolve PU foam: though rarely an issue for flower arrangements.
