I personally, would never even think of needing a sitter unless I was doing something really unpredictable, or some kind of ridiculously large dose. ie , 4th plateau dxm, 1000+ mics lsd, or 100x salvia.
If you are comfortable with lowish dose dmt, I am sure you will handle highish dose dmt really well.
I find it next to impossible to break through if I do not trust who I am with completely, and if I'm not in a completely comfortable headspace it makes the experience too confusing as I can't become fully "immersed".
IMO no sitter is a million times better than a bad sitter, unless you really need one, (unpredictable compound/massive dose) then time spent searching for a good sitter is probably in order, as I would not recommend tripping with someone you dislike, or someone who is a bad sitter.