Hi all, thanks for the quick reply. I'm using Lipo cell, and full charge would give me about 8.4V, and stabilise at 7.4V. It's very tricky. I have consider using linear regulator, but it would dissipate too much heat. Diode would only give me a fixed power drop, not an ideal application.
Running time is not actually a problem to me, (and efficiency is not a major concern), but weight is the constraint. I like to keep component count (and weight) down to as reasonably minimal, so using large heatsink to dissipate the heat is not be great idea. Hence I drop the linear regulator.
I have yet to check out the electronics store here. The reason I put a few options so that I could go for another one if they don't have what I look for.
I will try to post up my circuit design shortly. Thanks again.