Ideally I need to connect a sink waste to a soil pipe, it's 3 inch.
Does a 3 inch strap on boss exist? Because I can't find one.

And if I can't find a suitable boss....
Would it be a terrible idea to drill a suitable sized hold in the soil
pipe and just ram the boss adapter in?

By adapter i'm talking about this,
https://www.screwfix.com/p/floplast-...m-5-pack/89174

Also do we care where we connect it?
There's a few inch of pipe indoors under the lav, gut feeling is to
connect it as far from the actual pot as possible, are there rules?