Oh there's no need to worry about shadow eles, trust me you'll easily train a pack of frenzies up just hunting the right things
Just found my training doodles, this is what I did with the cats:
Deathwatch hatchings to 53.6
Corpsers to 77.2 or ettin or gaman will take them to about 80.6
At 60.1 you can try lizardmen or trolls to 87.3
Finish up with harpies, ogres and black solen warriors
Then you'd just need to work on magic resist and your pack is trained. But none of those mobs should prove too tricky for a frenzy. Keep them fed as you go and change spot to suit the lowest skilled frenzy in your group and you'll do fine.
Wenchy