HA! FIXED in P3D v3.4! Oh yes my holly old lady, I will bring you up to P3D Skies now  ;D xD

BUT, there is also a bad news, but first the good one:

After the fix i've stable Frames between 60-70 in the VC and Interior (outside around the plane in my Desert-Testing Area a bit over 100).

And now the bad news: It's the doppler-gauge. So you have to look about an alternative (CIVA INS?). I used the doppler nav in combination with the GPS so that the 707 follows automatically an (self created) flightplan. Maybe a NAV/GPS Switch helps, but this I have to test it first.

So, here's the fix - it's VERY SIMPLE:

1. Open the panel.cfg of the 707
2. Go to [VCockpit10] Section and place a Semicolon ; before gauge nr. 27.

It should look like this:

;gauge27=Captain_Sim.x707.dns!main, 1,1

After this the 707 should be FULLY OPERATIONAL and ready to fly in P3D 3.4! YESS  :D

A Second hint: Don't turn on the Weather Radar! This costs around 12 FPS.

I hope that Captain Sim will bring a fix for the doppler-gauge! This gauge can't be opened with FS Panel Studio (it says that it is an invalid gauge), I don't know why this gauge kills the 707 in P3D  :-?