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Read the Green Chip chapter
Inquiry, I am in a similar boat to you as a beginning counter, but I have avoided the heavy losses so far.
As others have pointed out, at our bet level, you can't use much if any betting cover. The hourly wins are just too low at green chip play, you have to bet pretty close to the count. I would suggest you re-read Andersen's chapter on green chip play*. I followed this advice on my last trip to Vegas, especially the part about limiting sessions and trying to be anonymous. My sample size proves nothing since it was just one trip, but I had a modest win and wasn't barred anywhere. I was spreading $25-$250 at 6 deck games using KISS III, so very similar situation to you ($25 unit, unbalanced count).
You should never play for 7 hours in one place, unless maybe the casino owner is your girlfriend :).
*ironic that he means low-stakes, when the Green Chip section of this site is for serious high-stakes players. Why not call this site's membership section Black or Purple Chip?
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