All the games work, but sometimes take 5-6 attempts to load. Is this normal - what's going on? I've only tried DSiWare from SD, so other roms could be an issue also. I tried multiple SD cards with same results.

If not,try to boot your DSi with or without HiyaCFW.
Hiya is not related to TWiLight.Doesn't Hiya only boot on SD cards 2GB or less?
Hiya is not related to TWiLight.
It can "live"" without and thats quite good.
And makes the boot of TWiLight a lot faster.
There is the Tool "Title Manager" thats for it:Hiya's like emuNand right? So I've to inject DSiWare, instead of launching converted .nds in Twilight?
There is the Tool "Title Manager" thats for it:
https://gbatemp.net/threads/release-dsi-title-manager-for-hiyacfw.518053/
Cool thanks, I'll look into this more. My only other concern would be the size of emuNand, unless you can grow its size.