You can simply adjust your batch size to 5.25 and enter the O.G. you measured. Keep adjusting the brewhouse efficiency until the estimated O.G. matches the one you entered, and you'll have your efficiency.
I measure my pre-boil gravity (and first runnings), but it's not necessary unless you are using the length of the boil to adjust for missing your target.
Conical 1 - Bye-Week Blonde
Conical 2 - Empty
Carboys - Cougar Killer DIPA
Secondaries - Sunday Night Hoppy Pale Ale
Lagering in Kegs - None
Kegged: American Wheat/Rye, Nut Brown Ale, Munich Helles, Belgian Stout, Resurrection Milk Stout, Bourbon County Stout, BLC
Bottled: Oaked Bourbon Porter
Planned: Baltic Porter