Adding tie down points to bed

I have two tie down points in the bed of my truck. (by the gate)

I'm not sure if there should be two more by the cab, but i have a roll out cover that may be blocking them.

my question, has any one had any success in adding new tie down points to the sides or mid way onto the bed?

 

Like the ones that are 3/4 the way up the bed?? I bet your cover is just covering them.

If you go rid of the plastic liner then you could just bolt some to the bottem corners im sure.