User blog comment:Kogath/Monster Hunter Generations Discussion/@comment-16331478-20160618121639/@comment-5569775-20160619015536

Not all the MV's are 15% lower in Yellow than they were in 4U; rather they range from as low a decrease as 6% to as high as 12%. Overall damage is roughly between 14% a 15% lower. At Orange, the Slam and Dash Thrust are actually higher by 1 and 2 points respectively than they were in 4U, otherwise, they are the same. At Red, the Upswing is actually a bit more than 5% higher, as is the Slam and Dash Thrust.

In regards to the heat gauge and WF, it's not like you have to wait till you are in Red to WF; using it Orange is fine as well, or rather, it's better than yellow. Part of the problem most people have with it from what I've seen is they work on getting it locked into red and instead usually overcharge it, getting locked into yellow. After it recharges, get in a few more shells to bring the gauge up a bit more and WF again.

Also, it should be noted that each Shelling type has a different Heat Gauge and that using WF lowers the current position of the Heat Gauge by about half of the current color it's in.