In all truth, You have very good coverage, I myself have recently joined the "Bald" club (although im at skin fade level, not completely shaved) and I start the top of my side burns linear to the top turn of my ears (not the top of the ear itself, but the first line at where the ear meets your head). That is a safe place, but its really up to you and what you are most comfortable. I have been blessed enough that my natural beard line is very symmetrical and requires the most minimal trim (2-3 stray hairs) So again its all about analyzing your beard as it progresses and deciding where you want to go from there. All in all you're looking fantastic mate! keep that up.