I suggest designing it in CAD and possibly sending it to be metal 3d-printed, which would be cheaper than a whole garage(I feel your pain on not having space... my carport is currently saturated with my business's equipment and I'd really like to build a proper workshop). In addition to less metal shavings around, you'll have access to different geometry which may help your design.
This prototype won't require any 3d-printed metal for now, mostly 3d-printed plastic and some easily made at home metal parts. I already have some cad designs, I have a garage AND dedicated workshop and enough equipment and parts to finish this, but only thing lacking currently is time (I need two jobs until at least end of this year, then it will be better). But thanks for suggestions.
I don't want to whine or excuse myself, I only give an example of why some inventions take a long time to mature into working design. I will make this, just not in a month of real time.
