i'm dead-set on tailgate up!..... (verified on downhill coasting test!)
 

I tried tailgate down on a steep 3 mile mountain.The first time going down,tailgate up in neutral, i gained 17 mph.The second time,exact same downhill coast speed,tailgate down, i only gained about 10 mph.i'm convinced!!!:thumbup:

Next, i will try grill block and airdam. This is on an '87 Toyota truck,5 speed

Quite a difference.

Sweet! Will you be putting an aero topper on to test? That would be interesting.

Why don't you buy a $12 piece of 1/2" OSB and just cover the rear most 4' of your bed. Sort of a cheapo half Tonneau cover thing.

Thanks for this! Someone at another forum was just asking about this, in his old Toyota truck.

what's osb,where do i buy this?

Google says oriented strand board, aka chipboard, plywood etc.

OSB is the stuff they use for building houses, I think it's better than plywood in that it does not delaminate. It comes in 4'x8' sheets and you cut it with anything you'd use for wood. It is available at any local lumber store catering to builders. The 1/2" is usually 7/16" thick.

It is all exterior grade, so it will take a long time for the weather to affect it, it is very strong compared to the coroplast everyone seems to be enamored with in this forum. You don't need to do anything to reinforce it if you just use it as a cover. If you want to put anything on top of it that's very heavy, you'll want to put some kinda frame work under it. If it works for you and you plan on using it, you can paint it to keep it in good shape for a few years. And for a quick half tonneau cover, you can't beat the price. The only trick is coming up with a way to secure it to the bed of your truck.

You should try the tailgate in various slopes... ;)