Sometimes you will need to cut or lengthen slides on brass instruments. I have seen this on a number of instruments over the years.
Recently I purchased a classic Conn 16E Mellophonium for some jazz experiments. I went ahead and “did the deed” this morning, and cut three slides. This was exactly what the instrument needed; the valve slides were certainly all too long.
The first instrument I had this done on was my old 500,000 series 8D; I had to have the F side cut down (too low in relation to the B-flat side, even pushed in all the way—common on 8D’s) and also have the third valve slide on the B-flat side cut down as well. This was done at the suggestion of Verne Reynolds, my teacher at Eastman, and he was right on the money on this one. If you have either of those slides pulled on basically any unmodified 8D you may want to reevaluate your tuning.
In contrast, on three other instruments I have owned that had high F sides I needed to lengthen the high F main slide. It needed done and really helped all three instruments.
In short, it is not uncommon that an instrument will need at least some minor tweaking, moving of pinkie rings, etc. Make the adjustments! They can really make a difference.