I don’t own a Boxford but I did fabricate a combined splash-back and motor guard using 3mm thick PVC sheet, which is moderately stiff.
I formed the bends using simple pieces of plywood clamped to it, and careful softening with a heat-gun. The joints are solvent-welded, reinforced by “angle-plastic” lengths made from the same material, and I think some aluminium-angle in one or two places.
You can bend thin sheet-steel by clamping thick boards to each side – laminated chipboard panels from old cabinets are fine for this – each side of the joint line. The boards keep the steel flat each side of the bend.
One way you can finish the edges for safety and rigidity, is with thin-walled steel tube. Cut a slit as wide as the sheet thickness along the tubes, bond them to the sheet with tack-welds or an epoxy adhesive such as car body filler. I have used ex-car brake pipe along short edges, and as I did not have a milling-machine at the time carefully filed a flat, a vice-width at a time in my case, along each piece until it just broke through the wall.