I adjusted my price feed to offset by -8% a few hour ago, which means if current price of STEEM on external exchanges is $1.00 each, my price feeding script will feed 0.92 into the system. The script will approximately update the feed price once an hour if price changed more than a threshold.
The offset is quite arbitrary so far, as I didn't figure out what's the best value, nor how to decide the best value. I'll probably manually adjust the offset in the future, when I feel need to do so.
This post is related, although I'm not following the algorithm in it entirely: @dantheman/boost-steem-value-by-backing-steem-dollar