Recommended method for connecting 40/50mm wastes to a soil stack

[Annker]

I'm looking for some advice regarding connections soil stack.

 

I have an ensuite and bathroom located back to back and the plan is to connect all the wastes (2xWCs, 2x showers & 2x WHBs) into a single soil stack which is located on the other side of a wall these two wet rooms share.

 

The WCs will share a back to back concealed cistern ,the waste from this will push into 90 degree bend then a 1 metre horizontal run through the wall and then connect to the soil stack with a 90 branch.

 

My question is if there is a preferred method of connecting the shower and WHB wastes to the soil stack. 

 

A neat option could be to combine the 2x shower waste connections to the stack along with the WC connection with this triple socket 90 branch.

 

Or is it better to use strap bosses or even these McAlpine bosses and make individual connection to the stack?

 

Also are there rules concerning shower/WHB wastes connect to a soil stack above/below WC connection to the stack? 

 

[marmic]

i will be interested to see replies as we'll be doing something similar soon - eveything into one stack / drain.  A tip I've been given is to have a dedicated waste pipe from shower to avoid the trap being 'siphoned out'  and a lovely scent entering the bathroom!