From: Vienna, Austria
Yes, Shortland is a good starting point, I used it very often myself.
Don´t worry too much about enemy air as long as the Allies do not completely control Guadalcanal. If you use Shortland only as the final stop
before making the run down the Slot, port attacks cannot stop you, and (more so in case you got a HR against heavies below 10k) the heavies suck
at naval attack. Everything else will be close to max range. A bit of fighter cover ofer Shortland should suffice for the moment.
What I did was:
When transporting troops: Loaded up @ Rabaul, set to "do not unload", set patrol zone with 0 days @ Shortlands, next turn the TF was waiting there.
Then I enabled unloading and set target Tassafaronga. With only 7 hexes distance usually this was enough to make the run at night, unload, and be out of range
again during the day.
When only transporting supplies Shortlands was enough as a base of origin.
Just be careful as soon as the Allies start using PT boats in the area. Then it might get time so switch over to SSTs, or use DD escort TFs.