Hi Mav -sorry, is that a male Mav or female Mav -can I call you Mavis?

Welcome to the forum.
I'm pleased we were able to help with the clamp design. Always looking for more tech articles to add to the site if anyone wants to send anything in -it's very often the basic stuff that readers want to know about, but are afraid to ask, for fear of looking silly. We've all got to start somewhere & we try to share as much info as we can.
There are several people here who produce versions of the disc brake caliper mounting brackets I first came up with to convert a Reliant axle from drums to discs. They seem to sell. Maybe not in huge numbers, but if the price is reasonable, they can take some of the hassle out of doing the job. So there's probably a similar market for ready made axle clamps. If you can afford to have them sat on a shelf in the shed, you might only sell a few sets, but they'd go eventually. Ebay will sell them quicker of course. It's hardly a unique design, but like the caliper plates, a mention of the site in the ad would be nice.
We usually use heavy gauge ERW tubing for our trike frames, so you'd have to make them from a similar thickness steel. 4mm would be good. They'll also need a locating tab to bolt to a matching tab on the frame to stop the axle sliding or turning in the clamps. If that's not supplied, you ought to point it out in your ad as not every prospective builder is experienced enough to think of such things.
If you go ahead with production, we're more than happy for you to advertise them here.