Glad I didn't post this question as I'd still be scratching my head. :) My manual says extend slides at ride height and then level. OP didn't state whether he has jacks or air leveling so that would help. Regardless, mine is air leveling and Monaco techs, (while they were still Monaco) said with air leveling, it really doesn't matter. The manual was written to pertain to "most" coaches. (slap head here). Anyway, to the OP - use common sense. If you're really unlevel, extend the slides, then level. If not, it probably doesn't matter. Twisting your frame while extending the slides may break your windshield, so use caution. Common sense says if you level, (using JACKS, not air)then extend the slides, there's little room for error in compensating for the extra weight extending from the sides of your coach.... Dennis