Hi,
Yes, the standard screen is too short, regardless of positioning, so is very noisy and buffeting. Don't waste cash on fancy / fancier screens. Get hold of a 3mm perspex offcut that'll give you an around 20 cm higher screen (you'll pick one up for next to nothing), then use an hot air gun to shape the perspex to match the existing screen contours. Trim / smooth the top corners to the shape you require.
Honest, it's easy!
You'll find you'll still have some buffeting, if you bolt the extension to the existing screen, so use spacers (washers will do, though I made perspex spacers) and make a 10mm air gap between screen and extension. The air flow through the gap prevents the frontal airflow from "rotoring"/eddying over the top of the extension. I found that I had to heat/bend the top corners slightly forward to completely eradicate buffet - easy with the air gun.
Really, this does work.
Pete W