Nothing wrong with peak hour. Board at Flinders Street you should get a seat. Peak hour trains that may b full would be between 5.30 pm and 6 pm or if the Melbourne Cup or football is on and it will not be packed all the way Let alone half the journey You will always get a seat if boarding at Frankston
10 minutes by bus to Frankston Station. That is 7 km. 3 Buses in an hour. 50 minutes average travelling time on the train to Flinders Street Yarra River Arts Precint MCG Mt eliza is 45 km from Mt Eliza I always take the Beach Road Not Nepen Highway and although the speed limit varies and drops to 60 km per hour in places It is very relaxing. Public Transport is good Get a time table and pick the train that is express between some of the inner suburban station. The buses and trains synchronize.
Hour and a half would be right - seriously consider driving out of peak hour or driving to Frankston station and relax on the train. Depends on your hours. The best way I've found is east link then monash get off at kings way and park at crown - you can save a lot of time. Of course you get hit by tolls nepean highway is ok as an alternative if you leave early (6:30)