to be honest, i would'nt call this 'hardcore challenge', well, anything but time of course, because diff 7 isnt that hard to cope with and usually gives an eassy start. To achieve victory - your biggest concern would be locating AI homeworlds, and for that you need all scouts you can get at beginning... after you have direct/approximate location, just go for it... Like i said... on diff 7 it isn't that hard, unless you run into heavily fortified planets, especialy early on...
About reloading - yes, i always tend not to, however that's inevitable when playing on higher difficulties (9 or so), because AI becomes significantly more threatening, and its not just about decisions you make, but also it's agrresion. If you manage to survive first incoming waves and build some economy - prepare to face struggle for endurance (depends on AI type).
And like other ppl have mentioned - much depends on map and it's type... even simple one can become much harder or eassier depending of it's layout, for example couple planets in a row leading to dead end, where you can simply gather resources without a worry of it being attacked.
Then again... this game offers huge variety of gameplay suiting everyones own tastes - so dont be bothered and just have a game that you enjoy most