The main menu panorama on Legacy took exactly 136 seconds to complete one loop. The speed in the mod is faster than that.

Affects 1.3. Due to the stretch fix, the duration has changed. It is now slightly slower than Legacy.

Legacy time: 136s
Legacy4J mod time: 164s

Multiply the current panorama speed/duration by 0.829 to get the correct speed/duration. (I'm not sure how this works exactly, but this might be helpful.)

I think it's now accurate in 1.3.1 version, so I'll close this issue

Yes, I just timed it in 1.3.1 and it is now exactly 136 seconds. Excellent fix!