I am installing 12x12 tile on a cement floor. It is a pretty sturdy floor. There are some spots that I just can't get the old linoleum glue up. It creates high spots of about 1/16 inch. Is it OK to use thin-set on this and place the tile or does it need to me more flat/level? Are there thicker thinsets that would act like a leveler? I'm reluctant to put down a leveler because I'm afraid it would flow down through the expansion joint area to the unit below mine.