Not sure what your Aigner rail looks like and what you intend to use it for especially on the bandsaw as besides extension tables, Aigner pressure module is an option as well.

First if your Aigner bracket is ~1 3/16” like mine (pic below), it will work with Aigner PM but not Felder extension tables. Felder brackets are wider, ~1 9/16” (see 2nd picture), and they allow the clamping bar below the ext. table to work.

Felder Brackets on Dual51

Felder extension tables will accommodate for less than perpendicular (to table surface) hole as they have height and tilt adjustments.

FYI, I mounted the Aigner bar at a height so that the horizontal sliding bar is above the table surface (see pic below). This is too high for the extension table. I am going to do something that will allow me to use both but I have not done that yet. It is possible to add set screws (bore & tap) to the Aigner PM bracket so that the bracket attached to the machine can be lower and perhaps will work with both. As a side note: Aigner PM will mount to Felder coupling brackets.

If you really want to go perpendicular a simple 90 deg jig composed of flat wood large enough to lay on machine surface with a 90 deg cleat mounted below should work. Cleat should drop down as much as needed and should be thick enough to act like a drill guide.

Hope this helps.