The alternative i mentioned does NOT need any modifications, it fits nicely in the recess in the clam.Or just fit original Hartwell latches from an EE Lightning or a Tornado fighterjet, which are plentiful on ebay…
These Hartwells will save you a ton of work by not altering all the bodywork to fit garden gate latches.
Morten
The lower part that attaches to the frame has to have a small tab made to mount it though and can't be screwed directly into the frame.
Attached from my own build down below.