How old is the frame? I have a Pace RC-200 F8 – designed for 90mm travel, but works with 100mm – was going to stick a 120mm set on and thought I’d check so called to ask.
Was told best not to as the frame wasn’t designed for that travel and the extra 20mm would add a bit more stress to the frame which again, it wasn’t intended for. They didn’t say the head tube would come away but they said it did increase the risk a bit.
Up to you, I decided against it s the Pace has sentimental value to me and I figured I’d be utterly gutted if the headtube ever did part company with the rest of the bike!