Join Date: Apr 2003
Location: Perlas ng Silanganan
Bikes: Custom Knolly Chilcotin Limited Edition Orange, Dartmoor Wish, KHS 7500, Custom built Specialized Camber, S-Works Road, Cannondale Trail mtb, Polini MTB
using your arm is not a very good measuring tool, since overall reach depends on so many factors, torso, arm length, etc., but is somewhat a guide.
Assuming, that you have the same body geomtery as me, I think the 3.5" length is a bit too far.
On my roadbike, if I measure it using my arm, the handle bar is about 1.8"-2" from my fingertips, but since the hoods extend far a bit more its definitely more than 2".
On my MTB, it's exactly 1" (center).
If you aim to get a 1.5", you must decrease your stem by approx. 38.1mm. But be aware that it would make handling more difficult if you decrease the stem too much.