Halara double-layer shorts sizing and length advice for size 18/20

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I’m tempted to buy some Halara shorts, the double layer ones. I’m 5ft 3in and a size 18/20. Any recommendation on size and length before I go for it?

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I'm a 16 on bottom half but quite tall. Bought L in the shorter length and they are great

I found the double layer ones too bulky and not at all flattering. But the denim ones are great. I reckon I'm more of an 20 than an 18 and the XL is good on me. The size L does also fit ( as in, does up) , but I prefer shorts to be slightly looser. I've got the high-waisted 6" ones, and a pair of the longer ones ( almost knee length). If you are younger than me with firmer thighs, you could go shorter than the 6". I'm also 5'3, but my days of hot pants are over!