Trestles have been around for a long time and have many different types of connections. Metal, plastic, 027 and O.
I will admit "bents" throws me for a loop.

 

Can you define what you mean by attach? Safe adhesive, nail type etc. to use?
T-Man, Bents is what I have heard used to define the Lionel trestle pieces (assume it supports and "bends" the track up and down the gradient.)

 

I am glad it was not a multiple choice question. It is a first for me.

To answer the question then. To secure the trestle on 2 inch foam I would wire it down, and underneath with a scrap piece of wood (popsicle stick), twist away at the ends. A stiff base might be necessary. Do it after the track is all done.

Or screw it to a wood base and glue it to the foam. Some glues do not react well with foam. Maybe a wood or construction glue.

 

Thanks t man.
Has anyone put a sheet of homodote down on top of the foam and cut out the track profile

 

These trestles are made of polystyrene, same plastic in age old model car/airplane kits, no? If so, super glue will adhere to them.

 

What is the point if you are using tubular track. It is a lot of work to cut out track angles. Just add the Homasote paint and done.

If you are still undecided, try u tube, there are plenty of examples.