According to Kevin O'Connor from London Power and Power Scaling, matched tubes are not necessary.  He states that matched tubes sound more crisp or harsh with increase amounts of odd order harmonics.  Also, matched tubes will drift toward unmatched over time.  He states that the asymmetries in unmatched tubes give a more warm sound and are more desirable.

These comments come at the bottom of a long web page of faq's.  It's worth reading the whole page to better understand tube amps and which tubes can be substituted.  See  www.londonpower.com/faq.htm.  The specific discussion regarding matched tubes is at the very bottom of the page.

I've bent a number of tube pins and have just bent them back and put them to use.  The pins are not brittle.   If a pin were to break off and stick in the slot, it would not be too difficult to push it out from the inside of the amp chassis.