Nope, I have never seen a dry ice and alcohol set-up. I have seen dry ice used for blasting welding slag of off welding fixtures in some car plants I have contracted with. I like the evaporation attributes of the product without leaving residue.
I still think liquid nitrogen would help in keeping your existing design cooler. Considering you already have a working design in a confined space, I would suggest building a sleeved reservoir around the vertical exit pipe as a secondary after cooler, outer cooler. Another suggestion would be to build a reservoir inside of your ice box and use the liquid nitrogen to keep your ice life longer. I can only geuss that your turbo’s cubic feet per minute does not allow enough SOAK time for the turbo air to absorb the cold.
Do you have room inside of the passenger side cabin to fabricate and install a reservoir around the pressurised pipe? Or, it may work better if you had a smaller dia. pipe inside of the existing pipe acting as a reservoir for the liquid with an electronicly controlled solenoid to control flow of the nitrogen.
It sounds like I am spending your money like the big boys in the new car sponsored programs, but I understand you are of limited fund$ and NOT suckling on any corporate nipple. These are just suggestions I am sharing from my years of Toolmaking for Tier one suppliers. FYI: I was a leadhand in the Largest Industrial Jobbing shop in Ontaro Canada at the age of 23, my experience is well respected amongst Engineers.
Just because something has not been done before increases my interest and motivation. I did not take sheet metal nor Autobody in highschool nor have I ever worked in an autobdy shop but I have built a considerable amount of show-wining autos and high quality replacement panels.
After you pull off some nice 9 second passes, I think you have the power to challenge the Big Blocks with your set up, but unfortunately I also know all about destructive testing, and the Tiger will show her limits too soon.
A camera in your Tiger would be awesome viewing ( much along the same thrill of running a Cooper S through Britain in the early morning, only better) and I can only imagine the sound would be great also!!

Rob Martel