Hi Mando,
I also would advise against using glue. If you don't want to use a pivot setup then I would drill the backs of the pedals and rivet them to the steel plate. Alternatively you could drill and tap them from the back.
The last thing you want is your pedal tread coming loose when you jump on the brake.
Here's a pic of the spring loaded setup I did.
The idea is that the pedal tread can pivot under the ball of your foot and keep it flat. With the low seating position in relation to the pedals the clutch pedal can get to an uncomfortable angle at the end of its throw. The pivoting treads fix this. I wanted the treads to pivot freely but sit level and not rattle when relaxed so I spring loaded them.
They are comfee to use and have good feel.
Cheers