The only concern I have about large T5 engines producing serious HP is the case through bolts, which the T4 has. Granted I doubt it is an issue for anything under 200HP, but once you build up huge cranks and stuff things start to break or reach max load tolerances.
Also check this out from Boston Bob:
http://www.vanagon.com/info/articles.../low-idle.html
Granted that is with the heavy 24mm wrist pins. The T1 rods will have 22mm which is much lighter. I still cannot figure if it is rod angle as Bob hints at or added pin weight or just the load of a large Vanagon to push around.
Just as a teaser one of the fellows listed here is doing a T5 and using Nickies 94Bs. I will be curious to see what happens there.
Personally for the first build I will stay with the cheap Mahle P&Cs until I see how this T5 works out. Again a relative unknown in some ways so I do not want to spend lots of money for a potential door stop. My huge concern is oil cooling for anything in a sedan platform. For a bus I have solutions, but for a sedan I have not done the research yet. But I like the non-doghouse shroud and no oil cooler in there plan and just use massive external coolers (two RX-7 coolers could probably keep a 911 cool). Once the iron 94Bs blow up I will strongly consider the Nickies T1 94Bs as a replacement once I find out how this works out.
I know I have said this at least 100 times by now, but I think for an upright configuration this is a really strong alternative to the T4 upright and pitiful AL T1 cases. Granted I still have some unresolved questions as I go along this journey, but this is pioneering so that is to be expected.
... I am still collecting parts at this point. And need to finish the Bus IRS conversion even to get a spot for the motor to go in. Busy days.
Take Care,