Nope...I don't disagree with Paul...
1Co 9:27 But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.
Verse is pretty simple...Paul preaches to others...Others who have their eye on him...
Paul watches what he does especially in public so he doesn't lose any credibility with those he's teaching...
Castaway doesn not mean loss of salvation...It's losing 'face' and being rejected as a preacher by those he's preaching to, thus, bringing the words of God to no effect...Nothing at all to do with losing salvation...
Check:
http://www.searchgodsword.org/lex/grk/view.cgi?number=96
It seems MOSTLY to mean rejected or disqualified. I wonder if there is another instance of its being translated cast away. But the difference between "cast away" and "thrown out" is, well, not all that clear.
To be complete, somebody says it might not refer to Paul's salvation but only to his qualifications to be an apostle. Hmmm.