Robert,
I have calculated the gear inches in each gear 1 to 8 on an Alfine 8 speed 39 chainring 18 sprocket on 26"/38mm tyre.
28.62, 34.97, 40.62, 46.21, 54.30, 66.41, 77.05, 87.69
If you increased the chainring to 42 you'd get:
30.72, 37.55, 43.61, 49.61, 58.30, 71.30, 82.73, 94.15
If you wanted to increase you gears by one step i.e. new first being where old second is, then you'd have to increase the chainring size to 48 teeth giving:
35.20, 43.02, 49.97, 56.85, 66.80, 81.70, 94.79, 107.88
I hope that's helpful, to workout the best combination you really need to work out the lowest gear that you will need for the cycling you do and then go from there.