I am very concious that the older instruments such as the conn 80a, - I use that simply as an example, - lack any adjustable slides the slides can be preset but not adjusted during play, there is no ring or trigger on these early jazz horns. I agree Mike, to improve correct slotting a slide can be adjusted to tune the note as we play it. This is necessary as the notes of the harmonic series are simply not in tune with each other due to the acoustic limitations of a fixed tube or collection of tubes such as a trumpet. So how do we play in tune on an instrument that cannot be adjusted as we play. The answer of course is by lipping. This is made easier in a looser slotting horn and perhaps the point of it. Are we seeing the result of legacy instrument design here. Loose slotting horns being the children of the jazz horns that required lipping to play in tune. A tight slotting horn would have been somewhat difficult to handle with little ability to lip. I put it to the members that the wide acceptance of instruments with freely adjustable slides may well have resulted in the widespread growth of tighter slotting instruments. I plead guilty here to building a house of cards from assumptions and table this for members to ponder upon.