I find "synpila" have been fine until they have a "Kokak Moment" and then lose it. A Synspila, being vegetarian and a sifter, don't usually pick fights but my female has finished them all!!
8x3x2 is big enough for a vieja.s and a pair of redtiger motags. . . personally i think redtiger motags are far beautifullier than the jags and are less aggressive. good luck.
I personally know it can work as i have all the suggested fish in together but as stated each fish has its own personality so it may take a few attempts with different fish to get the mix right.
Try to buy the festae and Jag as juveniles and the synspilum a bit larger than the others. Synspilum are more mellow but do stand up for themselves when challenged.
I'm giving up my synspillum for she's biting the fins off of my Oscar.
She's been a nasty fish since i got her, very territorial and now i'm fed up with her behaviour.
If you were in Holland you could pick her up.
My LFS is not too thrilled about getting her, but will take her in anyways.