Wephota FO5 and low contrast developer

[Fausto Saporito]

Hello,

I'm using Wephota FO5, an ortho lith(?) film, and I am trying to have some continuous contrast adapting some developers.
With this film is very hard to obtain a continuous contrast (better the FO3, according to the manufacturer).
Anyway, I got some nice, at least for me, results using 510pyro with 1+100 for 10mins: the result is a very high contrast one.

Now I am trying to get the opposite, taming the contrast.
I tried Metolal 1+150 for 8 mins and this is the negative (I am sorry but, unfortunately, I have no right equipment to do a proper large format scan)

It seems there's a sort of stain on the negative, but Metolal is not a staining developer, so I cannot understand what's happening.
This is the positive version

Thanks in advance,
Fausto