I'm a fairly big guy (200 lbs... maybe a bit more over the Christmas week !). On an Adamo Prologue.
I'm defo on the prongs
(If i sit upright, no hands for any reason when on the turbo THEN I sit back further into the main body of the saddle. But not when using the bars (base bar or aero bars)
Most I'll do on the turbo is 90 mins.
Outside am happy for 6+ hours.

The one thing I do do to stop the chafing due to getting hot'n'bothered down there is I do use some chamois cream on the area that rubs - if this isn't too much info - usually just around where the inside of my leg joins the torso (inc use a bit of the cream when using the turbo) - that sorts it for me .

Yeah, I'm almost exactly the same, prologue saddle, sat on prongs, chamois cream required & whilst I've gone over 90 mins on the trainer the saddle is often the worst part.

Had an ISM Adamo before switching to a Dash Stages. Definitely rode the prongs and had the same indoor vs outdoor problems. Suggestions to try:

Indoors, you don’t have the full motion of the bike relieving various areas of contact. Have you tried narrowing the prongs with zip ties for the inside setup? It may limit chafing if you can adjust the prongs off chafing areas while still being on sit bones.

FWIW, I love my Dash saddle but I still experience discomfort inside after a couple hours that would take me 4-5 hours to see outside. Some things probably never go totally away...

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