I think we need to have a on/off selection button so we can turn off pants or shirts etc.  there are some really cute thing in undies i would wear.  I hate that you have to have some kind of pants on under your skirt.  

Just a thought

You can still do it manually. Link to middle of page 2 of thread where the explanation starts. Get as close as you can in Customise, then Show Changes, then edit the file to remove the filename from ClothingLegMap= (and replace it with the filename of your chosen frilly knickers or whatever if you want them), save the file, click back to RLC and Cus => Don't Change => Cust => Show Changes to load your edited version onto the avatar.

Like it says in that thread, make a backup .ini first and make copies of myinfo.ini for various outfits so you can copy them to quick-change.