I one 110l tank i have:
2 x adonis
1 x candy
2 x BN
1 x common
the adonis and common are only there till they grow but give them places to take control of, personally im tight so use coconuts with a bit of plant growing on them, get them from any reptile shop for pence, the ones you see in fish tanks are normally five times the price,
just buy the reptile ones and boil them for about 5 mins to remove the colouring like with bogwood. then arrange the tank in different corners etc...
personally id also used an additinoal filter just to boost cleaness/water quality. ie a fluval 2+ or something capable of half your tanks volume so its enough help but not too much that ti hinders the main filter.
when mixing plecos i am also very concerned and watch them, as long theirs no serious fighting taking place i wouldnt worry too much, also when you feed, spread algae waffers/veg, in seperate pieces opposite ends/sides of the tank, so they dont feel they need to compete for food.
i may be talking carp but its always worked for me and i have several tanks with several plecos in, some agressive ie adonis are very terrorital and some peaceful. BN are/can be agressive little sods for the size of them.