I think the best reason to leave the strap button job to a luthier is that you can blame somebody else when the heel of your neck is cracked!!
As some posters have already pointed out, strap button placement depends on what you are used to, as well as what you like.
My favorite place for almost all guitars is not on the neck, but on the side of the body where the original poster's guitar has the wooden block.
Why do I like it there?? I dunno, maybe it has something to do with being short, yet built like a beer truck..... :lol:
Seriously, strap buttons on the bottom of the heel will 'flip' a guitar away from me, but buttons that are in the body (like the new Guilds), will position a guitar so it's 'just right'. In fact, that's one of the reasons I bought Scratch's '07 D55 (Padnah) back in October. I knew the strap button was at the optimum place for me.
A lot of Guild's have round, thin heels, plus a lot of Guild's have short dovetails that you can't see from the outside [folks, I don't know if this is just the '60's guitars that I've seen the necks off of over the years, like my '69 D35, or if applies to guitars from the later decades as well, I kind of think I've seen a neck like that from the '80's or '90's as well.]. As a result, if you put a strap pin into the lower part of a round, thin neck heel, if it has a 'short dove-tail', you may be running a pin through the 'heel extension' alone. To me, that is an incredibly weak part of the heel to be messing with.
In fact, we have a member here who had a '60's 312 that had a strap pin crack at the heel; it can happen, folks!!!
Anyway, if I had new Guild with the wooden block already in place, I'd put the button there, if only because most people will expect it to be there. That way, if you ever have to sell your guitar (it happens, doesn't it?), you have less of a story to tell.
easiest way to tell the size if its not stated is to just hold a drill bit up in front of the screw and match it to the size of the screws shaft..( not the shaft plus the threads)..
