Yes, that's a ton of head tube extension. Yes, he'll probably look kinda silly. But hopefully it'll keep the front triangle a bit stiffer to help prevent any weird behavior at high speeds.
Geometry for the geeks:
-62cm ETT, 60cm seat tube, 665 front center.
-72/73 head and seat angles, 65mm trail
-43.5cm chainstays, clearance for a 43c tire, 109.3cm wheelbase
-25.4cm (yes, 10 inches!) head tube
-11.6" BB height (Clif is running 200mm cranks)
-Canti/v-brake only - I couldn't talk him into discs!