Now for my 2 senses...
But you are correct about ANY fss (121, 118, 105) bird going on INPUT port 4
The FSS birds should work on any LNBF Input of the DPP44. However, some receivers can not see 4 birds (or even 3), as well as certain satellites. In which case you will need to adjust where the FSS and/or 129 satellites are connected on the DPP44 (and the DP34).
To keep from confusing the backyard installer with various versions of receivers, yes you should say put the FSS on Port 4.
For 1 receiver, you could alternatively use PASSIVE (non-powered) 4x1 diseqc and 22KHz switches if your receiver can control them.
With a single Dish receiver, you would not need or use the 22KHz switches...
Try 4 Sats to a 4x1 DiSEqC switch with single output to a DishPro receiver (not Dish Legacy receiver).
Hopefully the 4x1 can handle any power passing through it.

You could also use a 2nd 4x1 DiSEqC switch and connect to the 2nd output of each DP LNBF, and for the 118/119, you should be able to use 2 DP compatible splitters to feed 118/119 to the 2 DiSEqC switch.
Will it work? I have feed a SuperDish 121 & Dish 500 into splitters, then into 2 DiSEqC switches and then into a 622.
Just until I got my DPP44 to work with longer stringers.
Also only some 22KHz switches will pass the DiSEqC commands, however, I doubt that any Dish receiver will cascade a 4x1 DiSEqC switch with 4 22KHz switches for 8 orbital locations.
EDIT:
Just logged off, but hopefully I can edit this real quick.
I hope no one on the above posts think I am referring to them as a backyard installer (like myself).
We often have various opinions, and I respect (and value) your opinions.

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