I've never understood stop-loss, it seems to me that by using stop-loss, one is basically saying "I don't know what the fundamental value is and if it goes down I want to sell". Then, why buy the thing in the first place?
A strategy that indiscriminately buys more of an asset as the asset price goes down only works with an infinite bankroll. Such a strategy run with a finite bankroll will necessarily blow up eventually. Rigid stop losses mostly just increase the volatility of a strategy though (which also contributes to portfolio drag). A sustainable strategy harvests volatility of the underlying (mean reversion) and/or dynamically deleverages (momentum) as the price moves against the entry.
because your strategy/estimation looks like not perfect in this case, and you may consider to cut your losses at 38, and not become broken if it goes down to 20.