P2P using Force 4625 Subscriber Modules

We are using Force 425 with range extenders on 80 MHz getting 800+ on 16 km link for example, but I would like to get some comparison of 4625 and 300-25. I hope we all know that there are many parameters that are involving for the link speed. RSSI SNR and fresnel zone are the basics.
In my link on F300-25 we do have clear fresnel zone, very good antenna alignment (RSSI) (-55) and nice SNR (37)
With 4625 we do have same dish size 470mm so theoretically on ~6,5 GHz we should get better antenna gain +1/2dbi, also we do have frequency very clear from noise. So we should get better MCS. We are speaking about 80 MHz channel width and for this settings was my question, we should get RSSI -53, I hope SNR 40+, what speed can I expect on 8km ?