I don't really think that buying a fix amount of Bitcoin when talking about DCA is proper because to my own understanding, if you really want to buy through the DCA method, then you have to buy with a fix amount of money, weekly or monthly irrespective of the current price of Bitcoin, but if you want to buy a fix amount of Bitcoin, them you might  spend more or less depending on the current price of Bitcoin, but the major challenge with this strategy is that you will be forced to tamper with you emergency fund that would have been for your upkeep till month ending when you are expecting money from another source.

I just believe that the DCA method is design for us to buy in a comfortable manner, not in away that will make us to start doing opportunity cost just to meet up to the target of buying a fix amount of Bitcoin.