Yes the edge is still undercorrected. What kind of stroke are you using and MOT or TOT ? It is always best to stick with as large a tool as possible: it takes a lot of experience to get smooth results with a 1" lap.
Your 8" F4.5 only has about 4 waves departure from the paraxial sphere or 1 wave at center and edge from the 70% zone , so certainly no need for any drastic measures
You need to push the curve out to the edge and the centre may raise up in the process. Conditions are fairly cool at the moment so you might consider the option of making yourself a plastic tent around the polishing table and warm things up .
Don't be impatient to get a good figure so quickly. Enjoy the journey.