Wind Blockers - my experiences
Here is a repost I did about a year and a half ago:
I have tried both the Windblox and the Windrestrictor. Here is a summary of my experiences with both:
Windblox - Great deal for the money, easily removable (and can be stored in optional storage bag they offer), but the fitment of the straps, because of the slot locations, was way off. I returned the first unit, with markups on the blue plastic protective sheet, and asked if he could modify the design to allow a better attachement (also had the Cadillac logo engraved). I also mentioned that the Windblox was lower than the roll bar height, and that there was 1.5" clearance above the roll bar and suggested the patern be modified to at least the roll bar height, plus a little extra for some wind blockage. Tim sent a second prototype, with modified slot locations and an increase in height - he took my measurement of 1.5" clearance and used it all - it actually touched the top at the outer corners. I marked up this one and sent it back to him for one more final iteration (talking some off the corners and another iteration on the strap slot locations. My goal was to help him get a design that would be a better fit, more secure and best wind block performance. I did not hear back for 6 weeks and finally cancelled the sale. Tim may have gotten the final design upgrades finished and, if he did, it is the best deal out there - especially if you want to remove it for top up season. ***
Update September 2015 - My Friend Dennis has the latest design version of this and the strap locations have been fixed, but the clearance issues in the upper corners may still be an issue - it's real close to touching roof ***
Windrestrictor - Decided to spend the big bucks and go for the lighted version, with the Cadi XLR logo ("does your car return the favor?"). When I received this kit, if found the color of the clamps and the base (which hold the LED lights), did not match the brown color of the roll bars or the deck lid - they were two different colors - the clamps were grey and the base was a medium/light brown (not quite the chocolate color of the deck). I initially thought they sent me the wrong color kit, but they insisted that this was what they sell for the Tan interiors. Rather than return the kit for a refund, I decided to modify the colors myself with spray paint (yes, you can paint the leather base). The color I used was Rust-oleum Fine Textured Bronze (#7226). It is a perfect match. ***
Update 2015 - I now have my 2009 V and had different custom wording "Cadillac - XLR-V - Supercharged", and the black trim is a good match. Same deal on the tilt, mounted the LED base about 3/8" forward to eliminate the glare. ***
I also did the "tilt" with a couple of 1/4" felt spacers at the bottom of the roll bar (stuck to the Plexiglas), and moved the base slightly forward before installing it with the double sided sticky tape. This too solved the reflection driving (day or night).
And, because I could not help making it better/custom, I installed a relay in the system that turns off the brake light initiated glow when the reverse lights are on, so I could see out the rear view mirror better at night when backing up. I also installed a line that lights up the LED's when the courtesy lights are activated - this was a little trickier and required a relay and diodes to isolate the circuits, and because the dimming effect on the courtesy lights is caused by increasing the voltage on one side of the lights (they are 12V hot on both sides of the bulb when off).
Bottom line - I am happy with the Windrestrictor, as modified, to get the best system out there.
Finally, from a wind block effect, I would say that these systems seem to block between 50% and 70% of the wind, with the windows up (depending on speed). They aren't too effective with the windows down as they create their own little vortices with the air flow.
Hope this input helps you decide which way to go, and provides some insight on the options you have for a wind blocker that was probably requested by your wife or girlfriend - that was my incentive.
PAK XLR8
The windscreen will greatly help, but it creates glare when looking in rear view mirror. But it is easy enough to get used to..
) with tops down and windows up! 
