Inserting small molecule in lipid bilayer

When inserting a small molecule at the center of lipid bilayer, say using gmx insert-molecule, is it common (and acceptable) to replace one (or maybe several) lipids in order to insert the small molecule? I tried using gmx insert-molecule without any replacement (without using the -replace flag) but the molecule would not insert and there is no output file as a result (my guess is there is too much steric clash). My lipid bilayer is ~128 lipids in total (64 per leaflet). My molecule is about 15 angstroms long.