Thanks.
When chiseling, make thin but dark lines of whatever you want to cut out (in this case a neck pocket). If you have a pillar drill, drill out most of the pocket to the total depth of your pocket, minus one milimeter. That will make it easyer. If you dont, take your chisel to almost the line, just a bit away (like .5mm) and push down, do this round the whole pocket. Now make marks a bit deaper than you just made (if you can) parralel (i know not possible as the sides are taperd but you know what i mean) with the long edges of you pocket 1 chisel width apart. now remove the waste wood between the marks. Repeat untill Final depth is gained. I used a hand router to clean the bottom of my pocket, but you may not have one.
Im a bit tierd right now, had a stressful day, so if anything is unclear just say.
That guitar was designed so i could have an SG shape that i liked, the top half of an SG is deadly, the bottom half looks like it was destend for good things, but got squashed in prosess, all IMO of course.