Generally, a wee bit higher temp is indicated for still air units. 99.5 would give you some "headroom" for a mid day spike in temps when the ambient air temperature is highest.
If you push the temperature up to 100.5 there would be little to no head room for a spike. That's always my thinking anyhow. Erring on the side of a .5 too low may result in the hatch being 12-24 hours late, but it a fair enough trade off.
This also allows for the inevitable upward creep at day 15 and beyond when the eggs themselves will begin generating some heat of their own and contribution to an upward drift of temps.