Guild Bonus

Is there any reason to have only monsters from your guild in your formation?

I understand having all pyscho/covert/impulse monsters, there's a combo, but is there something similar for having all covert monsters if your guild is rancor?

The all pyscho/covert/impulse combo still seem to apply irrespective of your guild...

in your acheivements you get a bonus if you use cards from you own guild i think at max it is a 5.5% bonus to all stats

Can anyone confirm that?

I am in Tyranny guild and was hoping to build a Covert/Wyrm group, but I think I would stick to Psycho guys if there was a 5.5% bonus just for using them.

Cheers,
Tyanon.