I have to admit I don't have any louvers in the bonnet sides as yet, although as I say, I don't consider I have an overheating problem, it has never boiled nor shown any tendency to do so, despite having been taken up some VERY long and big hills. Grizebeck is one of the biggest and guaranteed to cause a problem if there a suggestion of lack of cooling.
http://www.barrowcentralwhs.org.uk/c.../grizebeck.htm
I just found this link, I must check my times up there, will be interesting to see how the Marlin compares with a pushbike!!!
My soldering may have done the trick but I need to gain confidence with the car, this will happen over time as I iron out the little snags one by one. I definitely enjoy driving it, even better in a way than my old Rover P6's except for the lack of comfort of course, more akin to a 4 wheel motorbike, which was what I was expecting. The response to the accelerator and brakes is now good and that is key. I just hope the fuel costs stay within bounds.
I am not rushing to make the louvers just yet, I need to make a tool first, but it will come, I have ideas...