I used PB Blaster, letting it soak for a couple of hours, then the tapping technique, then a half-turn. Repeat as required.
You also need hardened washers that fit correctly and won't let the bolt pull through - you want the bolt to be pulling the pin, not crushing the washer.
You could put a washer between the socket and the head to distribute the load more evenly.
There are professional grade pullers like this available - try Samstag Sales or AST, both on the web.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe