I don't think they actually did modify it a lot at all... If you look at the plans, they just put it in where it would fit. That's why the exhaust is where the propshaft would be and also why they put it at an angle. As for the safety: I am not aware either of any plane this size having safety (JSX pretends to be safe as they offer an optional BRS...). This is why our Beast One is designed as a BD-5J alternative with good stall characteristics, low landing speed, good longitudinal stability, a safety cell and a BRS. The safety cell is designed for 30G, while the nose incorporates a 2 feet crash attenuator design followed by a one feet severity reduction element (damper+antisnag) all derived from formula one by our chassis experts (final layout will start in September). As for the "good flight behaviour" of the BD-5: Longitudinal stability is below any standard while landing speed is rather high. If the engine fails it will nose up, which is fatal right after start. Some BD-5 pilots say "it is absolutely no problem, you got a full sencond to react", but decide on your own... You can see it with the Boeing 737 Max. There are only professional pilots flying them and they had apprximately 40 seconds to react to MCAS and still 2 out of 2 crashed... So, of course if you specifically train for the bad behaviour of the BD-5, it can be a nice plane with cool performance (until it kills you). With a safety record of almost half of the built planes already crashed (some statistics say only a third), it reminds me of the Starfighter where they interviewed a former pilot who said "you just get in and tell yourself you are better than the others, this will not happen to you".