""Would you establish a center line down the bows length? ""------
Yes, I like to mark center on both limbs tips at nocks (measured for length and squared across limbs first), and mark center both ways at center of riser. Then stretch a string from tip to tip and see if it aligns with center at riser. Adjust both marks at tips same direction to line up with center mark at riser.
""Then establish the sting notch locations based of center, 30” each direction for a 60” bow."" --- Done in step 1
Would you at this piont start tapering the limbs? Then file in notches for string and checking for twist and centering of string? ---- Yep here is where your squared across limb marks shine for getting nocks even,, and recurves usually have a shorter taper on limbs than longbows so I go about 7-9 inches from nocks , you can always take more if you want a different bend, but you can't put it back on.....
Sorry if too detailed, kind of assuming it's your first bow.
And welcome to TG !!