The FF fired at 540 m/s, vs. the FFM at 700 m/s for the M-shell, so I'd say that FFM will give pilots a good chance to hit. Three FFMs will not be too heavy - circa 80 kg worth of cannons + ammo weight. Granted, we must wait to DB 601N so the central cannon can be installed, the 601A was a show stopper in that regard.
WRT to Bf 109s wing thickness - Spanish managed to install the big HS 404 cannon on their Buchons, after fiddling a bit with wing internals.
You are comparing the velocity for different weight shells. Always a problem for German 20mm guns
Some sources say 600m/s for the MG/FF but in any case it was for 134 gram projectile.
The 700m/s was for the 92 gram mine shell but the mine shell lost velocity much quicker. actual time of flight to 300 meters was much closer than the muzzle velocity would suggest. At some point short of 300 meters the heavier shell would have passed the lighter one with the higher velocity. This is at sea level, at higher altitudes things aren't quite so bad.
The 92 gram shell lost (at sea level) 38% of it's velocity by 300 meters. The 7.9mm AP round lost 33% but since it had a higher velocity to begin with it actually reached 300 meters about 0.1 seconds quicker. the US. 50 cal only lost about 15% of it's velocity in the first 300 meters.
As the infamous mine shell will not carry either tracer or incendiary the Germans had to come up with a "standard" shell that would function with the same weight of recoiling parts and mainspring as the mine shell used. the result was a 115-115 gram projectile at 585 m/s that lost around 23% velocity (or bit less) at 300meters.
This set up may work perfectly well against 1939-42 bombers (at least most of them) but may be a bit lacking in fighter vs fighter combat. The MG 151 15mm lacked "punch" but it was a lot easier to hit with.
It was rated by manufacturer at 500 km/h. And by the user? Granted, insisting on the slim nose might gain a few km/h.
It was also listed as capable for 20 x 50 kg of bombs only, again by manufacturer - less than 1/2 kg of bombs per HP installed, and 50 kg bombs will not impress with their destructive power. No dive bombing means less accuracy.
The Bf 110 couldn't really dive bomb either. It was claimed that the do 17z could do 600kph in a dive. So strength and control; was already there for at least a steep glice bomb attack.
Bomb loads are iffy, If you have any manuals please post? Some sources claim two or four 250kg bombs and few claim or hint at two 500kg bombs. Depending on how they are hung 20 50kg bombs can take up a fair amount of room (B-26 would only hold 30 equivalent bombs even using the rear bomb bay). Unfortunately photos are rare?
Waiting for 601N, let alone 601E engines means it's already 1941? Perhaps it is better to have actual escort fighters for proper bomb trucks that can carry twice the bomb load, or more?
Trading of bomb bay space for more fuel is self-defeating here IMO.
The Do 215 certainly could not replace the He 111 or even the JU 88 for some missions. But since the 215 could outrun a JU 88A-4 it would seem that some use might be found for it.
If you go the four 250kg bomb route there may be room in the top of the bomb bays for fuel tanks. five 50 kg bombs stacked on top of each other take up vertical space. Or the ever popular aux tanks out board of the engines.
Maybe the bomb doors would need to be bulged? In any case the Mosquito was pretty much limited to four 500lbs until 1944 and even then not all bombers carried much more on every mission.
It might give you an airplane to use all those engines that were supposed to go into Me 210s
I am sure they found a use for them.
The Do 215 does not have to be as good as Mosquito, it needs to be that good so it can reliably evade RAF fighters. At 500 km/h for 5 minutes (say we believe manufacturer's figures) in mid 1940, it might evade Hurricane squadron that is about to take off, but probably not the other squadron that has 3000 ft advantage in height, let alone squadron of Spitfires. What happens once the 5 min limit is out, and Do 215s fly at 480 km/h?
Ju 88 as a bomber was an exercise in self-inflicted wounds, from the wrong position of wing/fuselage juncture onward.
While it may have to evade British fighters (Spitfires) over England, what it has to evade in the Balkans, and NA in 1941 are rather different, not to mention what it has to evade in Russian in 1941/42. Not the best the Russians have but the Average that the Russians have. With DB601Ns or DB601Es it might only be 15-25mph slower than the PE-2?