Looking for some advice.
Had same. Fronts on my 1200 with 11/16 non boosted master no problems but on stanza get a long soft pedal til just above floor. Hate it. Its got the pbr master and a booster.

Hilux non vented 4 piston front brakes with s12 rear drums.
no fluid leaks new rear cyls and shoes.

Ok reading and looking into this further gazelle had 15\16 mc, stanza 13\16 both boosted.
In 1200's and early z they were 11\16 and 13\16 non boosted and run similar set ups ok.

I ran these exact calipers on my 1200 with the 11\16 mc and 20mm rear wheel cyls to better balance rear braking. Worked great and good pedal feel and modulation.

Unboosted my understanding 13\16 would be similar but gazelle wheel cyls are 22mm.
So would this be the issue potentially? Necessitating a larger mc when using brake booster

Found a 15\16 pbr mc but rod length is totally different too.
Speaking with baz could go to 7\8 but pbr has 3 brake lines jap only 2 and different sized rear brake mc fitting.
I can't make brake lines unfortunately