Typically i 3x my opens pre antes, and 2.5x with antes.
3b size i tend to 3b 3x pre antes and smaller after the antes depending on my position.
This is back to front surely.
Raise more with antes less without.
very few people call junk with pot odds created by smaller raises - and if they do its a pretty bad spew
therefore if 2.5x is effective - then use it - obv means you are donating less if you have to fold
finally - if you are 3.5x or even 4x'ing - your competant opposition will think you are terribad - so dont do it!