I'm leading a 'Little Big Band' with a crooner vocalists- e.g. we're playing big band charts (custom arrangements) , but the band is rhthym section, alto & tenor saxes and trumpet & trombone.
I play lead bone in a different big band, on a 1935 Conn Vocabell trombone with a Marcinkiewicz ET1.7 mouthpiece which really zings in the high register. (The blending in our trombone section is err, unusual, so it seems to work ok)
But in the 'little big band' I'm trying to cover a wide range of the trombone parts as there are often low register notes that are integral to the pieces (think Buble's Feeling Good or Cry Me a River, others as well) - and I'm just struggling to get a good tone quality out of the peashooter at that register, with that combination.
I have a Conn 88H, which I normally play with a Shilke 51D ,but that's quite a heavy, dark blow for jazz.
I also have a Holton TR181 bass trombone, but I don't think that will work too well

Just wondering if I should swap the mouthpiece out on the pea shooter or the Conn 88H, or if I should even be looking for a different trombone. (I'd have to look for something used as I have a budget of about £600 I can spend on something and it's not always easy to find good used trombones where I live, certainly nothing I can test drive easily). Or maybe I just need a lot more practise still!!

Anyways, I welcome your thoughts? Thank you!