Need some advise on bolt extraction.

When my three link mount let go, the second diff mount bolt (was using one of the cover bolt holes) sheared off. I tried small RH drill bits with no luck. I think this is a metric grade 8.8 bolt so it's pretty tough.

I've ordered some 1/8" center drill bits and then some LH bits. I also have easy out's once I have the hole drilled.

Are there any other techniques other than:
1. Center drill
2. LH drill bit
3. Easy out

??