Here's what DeckX (Canada) uses for their steps:

Step Decks
Width: 102 inches
Length: 48 feet
Rear deck height from ground: 41 inches
Front deck height from ground: 59 inches
Bottom deck length: 37 feet
Top deck length: 11 feet
Trailers equipped with air ride suspensions

As you can see from the picture, the tandems are CLOSED.

They were just the std. closed tandem like on a van or tractor for that instence.

Anything that has pieces over 30 feet you'll probably overload the spread. Of course palletized won't matter.

Not true, hauled 40' sections of drill pipe before and casing you use load lev. and have hauled mach. that were 32'-37' before and never over on the spread you have to know which end is the heavy end an spot right on the trailer.With the 8' deck you can't get enough weight on the front which makes them more difficult to load and puts you heavier on the rear.With a 8' deck you also have to run with the 5th wheel all the way back so you don't hi the neck on the trailer with your tractor frame or flap hangers not to mention all the debris that gets on the 5th wheel plat because with a 18" pin it does not fully cover the plate.I would have got a 36" pin if I could have but they don't make them for a 11' upper deck so I got the 24".

I have an 18" kingpin it definitely covers the whole plate. I had a load in Feb that I couldn't take because of my 11 foot upper. If I had an 8 foot upper it would've been no problem. The load was one piece and about 9 feet high. It was also very long.

Not all freight can use the upper deck, or load levelers.

The final spec of my Wilson
 

Based on all feedback I got here (thanks, guys) and extensive research on the Net, here's what I decided for the final spec:

48 ft long Wilson RoadBrute combo (Model: CFD-900)
10 ft upper deck with a 24" kingpin
38 lower deck
34" deck height when loaded
17.5" tires with steel rims
CLOSED TANDEM with 61" spread (wanted to make it 49" but then the king-pin to rear axle assembly would have been over 41')
Fixed tandem (no slider); the rear axle center is at 31" from the rear of the trailer
No rear impact guard (was required with a rear axle slider)
Steel coil package

Price in U.S. dollars if I pick it up at the plant in MO: US$31,264. The weight will be just over 10,000 lbs.

This trailer will be legal everywhere incl. California and Western Canada. I'll be able to take up to 43,000 lbs over 4 ft space; up to 45,000 lbs over 10 ft space; and up to 48, 000 lbs over 20 ft space. Closed tandem like this is rated for 18,000 kg in Ontario, Canada and 17,000 lbs in Alberta, Canada (multiply by 2.2 to to get LBS). My tractor has a 52" spacing between the drive axles and a 230" wheelbase.

>The group can have 40,000, but each individual axle cannot be more then 20,000.
I don't think I've ever had those axles scaled separately.

Roof fairing when pulling a stepdeck
 

I have a full size removable roof fairing on my International 9400. Do you guys think I should lose it after I start pulling the step? I installed the fairing last year as I've been pulling dry van trailers exclusively ... The dealer said the darn thing weighs about 400 lbs. Would be great to shave off that much weight off the truck. Fully fueled, with my inside, my truck weighed today at 20280 lbs (11720 lbs for the steer axle; and 8,560 lbs for the drives). That's with the fairing and the steel rims on drives (I have alcoas on the front only).

I would lose it there is now benfit to having the roof fairing when pulling platform's.It will also buck the wind I have that problem with my classic its a condo and it play's hell in the wind.I was considering changing the top cap on mine to a flattop to help.

I would get rid of it tracer. I have a 770(full height volvo) and it really does play funny in the wind. Worse then with a dry van.

Congrats on beating "dry van disease". There is hope after all.