"I mean, what is 1.035 in terms of a Portsmouth rating; and what is 1.045 in terms of a Portsmouth rating? Is there any valid way to equate them?"

Based on 1hr you have a 36 second range for 1.035 - 1.045. Some clubs use a conversion factor from SCHRS to Portsmouth Yardstick to score with monos, but I personally am not convinced by this method. Don't forget the conversions will be to UK portsmouth yardstick. I haven't seen one for the US ratings. You could work from 104 range to the F18 rating to get an approximation against the US yardstick.

Cheshirecatman