Petti Struggles: Where to find the best petticoat? Average petticoat length?

[darling-mermaid.livejournal.com]

Petticoats are extremely important, but there a lot of details I find unexplained when scrolling forum through forum! And, as 2016 is coming to a close, I'd like some brand new feedback.

I've been saving up to invest in a really good petticoat. Although, the question is- which brand (and/or offbrand)? As well as: how long should the average petticoat be? I'm aware petticoats are supposed to be shorter than the actual skirt- but how do you avoid the dreaded lampshade effect? I've heard many things about Dear Celine, Classical Puppets, and brand pettis such as Angelic Pretty or Baby.
Then, we run into the issue of custom sizing. Does the average Lolita choose custom, or free size? And, if custom- is it more than just a waist measurement? (ie: desired length of petticoat)
Any opinion on which is the best? For example: I own the Angelic Pretty Jewel Marine JSK (Length listed as 84cm[33in] ), which requires a A-line petticoat. Any suggestions, or comments on the works of petticoats?
*Feel free to add in your favorite/preferred bell-shaped petticoats as well.