Some summer timetables are not available yet, for example Italian timetables. It's also quite far in advance (more than 3 months). try again in April or May and keep an eye on www.trenitalia.com (for Italy), where Italian timetables will be visible first (although you can't book pass reservations there).

Just use a same-same weekday for april or may-times will not change very much after. Plus that all this nervous planning to the minute is not the real InterRail spirit-there will always be other ALternatives or maybe even your plans change a lot. Who knows.