TriMed, it doesn't matter what the multi-type is w.r.t. single engine performance if it's a Part 23 certified aircraft. They all lose ~70-90% of their two engine performance. Best you can do is start with something massively overpowered under normal circumstances so that whatever power reserve is left OEI is still sufficient.
NB. I had an in flight shutdown in that Panther Navajo a month or two ago when L.Eng. #2 Cyl injector line broke. At A090 I needed nearly max power to maintain altitude, at A080 climb power was needed, and at A060 I could maintain altitude at 75% power at Vyse+5. That's with an extra 25 hp above factory equipped.
On a side note, the EDM paid for itself that day. I'd been watching the EGT & CHT for that cylinder deteriorate for a while and was considering returning to base. All other EGTs & CHTs were normal. I thought it had a blocked injector. When the line broke I saw the EGT drop to 0 deg & CHT start reducing. No fire or smoke and, thanks to the EDM, I knew it was a particular cylinder. Didn't know at the time whether it was an injector, blocked/broken line, or swallowed a valve, cylinder break or what, so elected to shutdown the rough running engine and started back to base. With the EDM I could monitor the working engine's temps really accurately. I descended in stages until the live engine's temps were able to be maintained where they would normally be, and then airport hopped back to base. I had nearly full tanks & wanted to reduce that a fair bit before putting the wheels down. Fortunately there were so many airports in the area (East Coast Florida) that I was able to stay within a minute or two of a suitable strip the whole way back to base instead of circling the nearest & then landing.
Without the EDM to get some idea of what failed, and monitor the live engine I'd have landed at the nearest airfield so having it saved the owner from the expense of a grounded aircraft away from base + finding maintenance + transport + ferrying afterwards + the hassle factor.