I rig to "sort-of" IGFA specs but not for record purposes. I certainly don't handicap myself with regulation length shock tippets. I have used heavier class tippets in the past but managed to bust a couple of flylines - admitedly not 'purpose-built' blue water lines with the kevlar cores that would probably test a lot stronger.
I'm not sure of the IGFA rationale behind the actual specifications.
When sight fishing, look over your shoulder from time to time, you never know who's behind you