doubling up is not a good practice, but i do it more often than i would like. RE sector comes to mind right about now (ng). there are also times where i purposefully scale into a position in 2-4 blocks. while that could be considered doubling/triple etc, i do not. those instance are for when we are approaching a turn. for ex purposes i will use a low pivot since that is where we are now.
as we come down i cut back on shorts and move money into longs. often times i get fully long too early. while i am losing money on the longs that i am buying as we contine to drop, the shorts that i still have help offset the losses in longs. perhaps someday ill be able to do better on turns but for now the acct generally comes to a standstill while i shift from long to short