D fits better with the "fret" markers and the rest of the instrument so perfect knob IMHO, but C would be 'kin hilarious with the line right across the top like a John Thomas.....
I would try starting from bare wood then make a kind of handle with a piece of string through a neck bolt hole and carry it around for an hour or so banging it carelessly into things. Probably do that bit outside so you don't trash the sideboard
Then a coat of light brown stain and rub it off with a pad so you don't wipe it out of any dings. Repeat until you have the depth of colour you want then finish with a matt lacquer or wax.
I've never done this so I'm hypothesising (making it up), but that's how I would try to do it.
Inserts and neck screws, is there an optimum size, M5 seems about right from the old eyeball, M6 feels too big and M4 too weedy, but what are you using? I know @Jabba_the_gut uses them on his builds.
Our heating is due to be replaced urgently, so hopefully the big oil tank will go and my available space for "workshop" will double and a bit. It'll still be in the cellar though.
See Bench Build Diary for pictures, if they're still there!
I was worried that the rock like richlite had finished you off. I was getting out the torches and sharpening the pitchfork before rounding up the mob to go and find Fleabag
Dulux have a range of pigmented wood coating...
Stunning bit of wood there, could you use something like chopping board oil?
Sorry, just remembered you wanted to lacquer it afterwards. Or not lacquer just oil it occasionally?