I have a sample size of 167. In addition to DV, IV, and a moderator variable, I would like to use 6 variables. Is it too many? How do you determine acceptable numbers of covariates?

Also, less covariates can be a better study model or a worse model? I appreciate your opinions.

It is a hierarchical model, 1)covariates, 2)ID, moderator, 3)interaction.