[1tonne]

If I remember rightly (so I could be wrong), the standard PDI cylinder has a slightly smaller volume than a normal one. The bore up version is actually very similar to a stock cylinder volume (if only just over).
Also, you are looking at using a 6.08mm inner barrel. This is wider that what most of us use and is less efficient. 430mm would be good if the bore size was 6.01mm-6.03mm. I would advise trying a barrel of around 390-410mm because of the air loss.
Though you may not even see much of a difference between a 430mm barrel and a 390mm.
If possible, get yourself a 6.01mm barrel. They are way more efficient and none of us here have been able to see an accuracy difference between bore diameters. The only difference is the tighter bore will give more fps and this can contribute to better accuracy. But if a wide bore barrel and a tight bore barrel are both shooting the bb at the same energy rate then the accuracy should be about the same.

 

[1tonne]

I just realised that going off the ratios I did, the matching barrel length for a 6.03mm is actually 400mm for a 0.45gm bb. Not 430mm. Since your cylinder is wider, I would only recommend going up to a 420mm inner barrel if it was a 6.03mm.
Though if you already have a 6.08mm PDI barrel, you may want to cut it down and then make the inner cone again with a rotary tool. With the 6.08mm, I would definitely go with 390mm just because of the extra air loss. This should give you about the maximum possible energy for your system.
If you do only cut the 6.08mm down to 430mm, then that would be fine too. It will still be accurate but the 390mm barrel would have most likely got you about 0.05 joules extra energy. So not much.