Proper bankroll size for low level NL headsup

[cognito20]

Hi everybody:

About how many buy-ins would you think would be the proper bankroll size for someone who was thinking about exclusively playing $5 and $10 no-limit headsup matches on Poker Stars? As far as my playing ability as compared to the average player at that level goes, I'd probably give myself about a 7.5 or an 8 on a scale of 1-10 (I've been using Harrington's basic headsup strategy from HOH2, with a few minor tweaks and randomizations thrown in to mix up my play - and have been doing OK with it in a very limited sample size of matches...my current record is 42-23, exclusively at $5+0.25 level). Due to the inherent variance and swinginess of headsup play, I would obviously assume you need far more than the normal 20-30 buyins a good player would need for a SNG or MTT, but approximately what is that number? Any help would be appreciated. Thanks. :-)

--Scott