I recently acquired a new 88H (current model)

with the fixed leadpipe. My impression is that the stock leadpipe is fairly tight and I would like to be able to try something a little more open.

Is this a fair assessment of the stock pipe?

What era?

I wouldn't classify the 88 as tight, it's more open than the stock 42.

Should be more on the 'open' side, as Aidan indicated, depending on era to some degree. I was told by Ben Griffin when he worked there and I was switching to more of a Conn style instrument that a ~2.5 in their nomenclature was roughly similar to what you'd expect fro ma Conn. Their VE and RS pipes are in that ballpark too. However, what feels 'open' can vary from person to person and horn to horn. If something is too open or the slots are really wide, it can feel difficult to play because you have to know exactly where you want the note... little room for forgiveness. Whereas with more centered pipes, you will either chip the note or the slots will be more in line with what you are expecting because the slots are 'smaller'.

Fortunately, Conn pipes are pretty cheap. A new Marcellus pipe (which is the more 'open' 88H pipe Conn offers) is $30 from Hickeys. The Remington pipe is cheap too but it has a different receiver. It's supposed to be the same otherwise as the S pipe.

And if the more 'open' pipe doesn't work for you then you can try the other direction too. On my Shires, which is similar on paper to the 88, I've been using a 1.5 on my 547 slide recently and it's been working quite well. But I also play a relatively small piece for the section work I've been doing (Shires 6.5AL with an Elliott 104N rim). That setup strikes a really nice, easy to play balance while still being broad and not too bright, which has always been the challenging part for me.

The stock S pipe is very open.