Do you secretly work for Irwin? 
No, i sell fish and chips

I've tried the grips method before on a mk3, it still wouldn't budge.
Mk3's also have loctite put on the threads, so they are real f**k*r to remove.
Those irwin extractors always work, without fail.
I usually don't bother even trying to remove the bolts with an allen key socket, they always round off.
I use the extractor to remove the bolts, then clean up the head and re-use them.