I also experimented with a seal on the bottom of the bed next to the cab, in all positions (short seals on ends or in middle) or all the way across, it added drag. It did add stability to the back of the truck. That coupled with a behind the front grille block in the upper half of the upper portion of the grill, made for a very stable some pretty crappy conditions... aka high winds on a bridge I cross daily. The first thing I noticed when I pulled both off (grill & lower horizontal bed seal) was the loss of the stability gained by both seals... it was nice.

 

here is a link to my trucks 11 yr makeover I did years back, there may be some other things in there you can leverage...

(1) 11 years, 345k on the clock, time for a makeover... | Cummins Diesel Forum (cumminsforum.com)

and the aero effort...

(1) MPG improvements through aero mods | Cummins Diesel Forum (cumminsforum.com)

 

You have certainly been giving this a lot of thought and experimentation. I look forward to getting time to study this later.

 

I want the most out of both trucks... and yeah I might have had too much time on my hands lol

 

I have the flex-a-lite Efan in my 05 and have had it for about 5 years going now. By far one of the best upgrade I have done. Yes the temp swings are noticeable on the gauge but if you read them from the ODB port they are not. It did help a little on the gas mileage and power but I wasn’t really looking for that. I was more going for the cooling of the engine results since I live in S.E.Texas. Temps here have been 100-108 this summer and my gauge hasn’t gone over the 1/2 mark at all even in traffic. I don’t do any heavy hauling or stuff like that alot but when I do I can tell the difference with this. I highly recommend it.

 

Great, I appreciate your Yea vote 'FOR'
Thank you... \

I am still looking to find a lost $350 dollar bill lying on the sidewalk and I'll get hooked up and post my review of the system.
Esteemed member Mangoon suggested that many reviews on here over the years but I am not finding many within my search criteria. Nor even a lot on Google or Bing for that matter other than Flex-A-lite website and as you can guess, they are positive salespitch.

I am not hauling much, heavy, or far... but I will retain the original components (clutch fan and shroud) incase my mission profile should change, I could restore it if needed.

 

OK, three months later and I broke off a Black Friday deal at JEGGS and bought the Flex-A-Lite eFan kit. It arrived today.
I will retain all my factory shroud and clutch fan in case I choos to revert back to factory parts

More coming soon, Same BAT channel. Same BAT time. dunna dunna dunna dunn dada BAT MAN!

 

is that a single fan?