The 1-1/4" and 1-5/8" both will work... BUT there is one consideration...

The carb needles... With either of these options they will be hard to access...

With 1 1/4" standoffs you can use 1/2" plywood spacers to get them out where they work well...

1-5/8" standoffs need a 1/8" ply spacer to get the rear needle out enough to access.

This is how I did it with the 1-1/4" standoffs and 1/2" spacers.

This lets the back of the bottom of the cowl sit flush with the gear slot.

It's possible that DA sells 1-3/4" standoffs too and you wouldn't need any spacers...