It is weird that it did not post a larger image. You went from 20 MPG to 30 MPG? That is a 50% improvement and should be a huge deal, I just wonder what else attributed to the increase. I doubt that the grill block accounted for even 30%, especially since you had 0% with a 50% block. Also, that is technically a 100% lower block. Your upper is still open and you might try blocking that, people do not seem to have problems with 100% upper and lower blocks, at least unless it is warm out.
How much of a difference does the block heater make by itself and how much from the grill block? Did you change your driving techniques? Also, I really do not know how putting insulation in the front of your engine compartment makes the back quieter.
I hope that I do not come across as a meanie, I am glad that you are on the site, participating, trying to improve your mileage, and sharing your experiences with us. I think the foam insulation looks pretty good and that most people would never notice. The colors match pretty well. However, I might expect a 5% mileage increase, from 20-21, not 50%, from 20-30.
Good luck, I hope you continued success.