If it's not too late to add a reply:
Book figures for best glide speed are quoted for max all up weight. As aircraft weight decreases, so will the IAS for best glide range.
Also, best glide speed decreases as altitude increases.
So if you go up to 3000 feet or so at less than MAUW, best glide speed will be several kts less than the book figure.
To add something else to the thread - has anyone else here been embarrassed when teaching best rate versus best angle of climb attitudes, and found that there is little or no difference in rate of climb when using book airspeeds?
[This message has been edited by Oktas8 (edited 13 May 2000).]