Truckbed cap question

[hat_man]

Hello again

Just another silly question for you all.

I am now thinking of a bed cover/cap to help with the bed area. I know a cap of some sort will help the most but could be rather expensive. I have an idea for a cheap "tonneau" style cover but, in the opinoins of all you here in the forums, would I possibly see any gains from a tonneau style cover or should I just bite the bullet and try a cap. I realize I'm not going to see 3mpg from cover but even 1mpg would be an improvement. I drive anywhere between 70-120 miles a day for work with 80% of it at 55mph, usually on 2 lane blacktops. To take the interstate costs too much in tolls to make much gas savings worth it.

Thanks for the advice

Hat_man