I was up north, Newcastle, and wanted to shift some weight off the rear rack ,
a framebuilder knocked one out in 48 hours , for me , of steel ,
It mounted to the ends of the cantilevers, and the bolt hole thru the fork crown.

that was 1991, Its still good..

yes I know how, but you need someone there, to sort it out.

there is a knock off of the Blackburn MTN F, they will serve as a substitute
for the hoop of a Blackburn low rider rack, there is a china copy of that 70~80's
classic too.