I've started several games with the following configuration:
Realistic 80-planets
Difficulty 9 Golemite, Avenger
Difficulty 8 Neinzul Nester, Avenger, Hybrids, Advanced Hybrids
High ship caps
And I can't ever seem to make any headway. It took me several attempts to even live through the first wave (@10 minutes), and on that game the next wave at 45 minutes is 1000 bombers and several hundred other things. There's MK III and Mk IV planets blocking pretty much every route.
Here's a sample of a first wave. The first group is from the Golemite, the second group is from the Nester:
194 MLRS II
233 Bomber II
276 Frigate II
~2 siege starship II, ~2 raider starship II, ~2 flagship II, ~2 Bomber Starship II
2 minutes later
282 Fighter I
246 Raptor I
2 Light Starship, 1 Siege Starship, 1 Bomber Starship
Just out of curiousity I totaled up the resource counts. The Golemite's attack group alone cost 955,400 metal and 1,013,400 crystal. I have 590 and 636 income respectively. That's with a -20% Golemite and +20% Human boost to resources. 10 minutes gets me about 350-400k resources with that rate, so counting engineers, reactor costs, etc. I'm probably outmatched 3:1 just on that wave. It is possible, just fantastically difficult even with extreme micro.
I found that heavy beam cannons were mandatory, as siege starships were too big of a target and didn't have enough firepower to cost effectively counter the Raid and Bomber starships.
I also found that i needed at least 2 forcefields defending the command station & cities, but more than that was a waste; if I tried to turtle i'd just run completely out of things with guns.
But I'm curous what else I could possibly do. It's generally not a problem of the command station getting blitzed, but mostly one of just living through the waves. The time I beat it was mostly because the Golemite rolled a fairly gimp wave (2 MLRS groups and a Bomber group.) My extra unit is Space Tanks, which I've been using instead of bombers because of their anti-bomber capability. Honestly, I don't remember difficulty 9 being this radically hard way back in 3.0...