I am still developing my fire making skills and I just got a hexamine stove and haven't yet played with hexamine, but I think basic fire building techniques would still apply, meaning that the hex tab should be under kindling (pencil sized) wood with progressively bigger pieces going up from there until the fire is hot enough to catch the bigger fuel.

My guess is that if the hexamine was under a good sized piece of wood only it would be like trying to ignite a big log by lighting a mini Bic under it...a waste of time and effort (and probably a scorched thumb!)

I don't know how the hexamine fares in damp conditions. Wetfire tinder might work in a wider variety of weather. Unless of course you regularly pack hexamine, then it makes sense to use what's available. Although Wetfire doesn't take up much room. But as I understand sometimes Wetfire can "wear out" if it's old, so you would want to replace it on a schedule with other "perishable" kit.

My two cents <img src="/images/graemlins/smile.gif" alt="" />