I don't overlap the elastics instead a have the ends touch each other. This means I cut the elastic the exact length I need nothing extra.The reason I don't overlap the elastics is to eliminate bulk and since it is stitched through I am not worried about it coming undone or shifting. I do overlap elastic ends for elastics placed in casings. Most patterns will give you an amount to cut for each area and they usually include an overlap amount (I subtract that out). But, you may find you need to adjust the length depending on the stretch and memory or return of your elastic. If I'm working with a questionable elastic I will sew up a sample and make incremental adjustments. I have learned a more calculated method of finding percentages/ratios and such but I can't be bothered by this and it gives me a headache.
The elastic is sewn together using a wide zigzag with a tight stitch length (close to buttonhole stitch length).
Next, I marked the leg in four equal sections. I learned from patternschool.com that elastics placed in modern stretch fabrics should be sewn in by stretching the elastic over 4 equal sections. this differs from information found in basic pattern-making books which have you leave the front elastic un-stretched in 1:1 ratio and the back stretched with remainder of elastic in a sense creating what I feel a bubble butt. This un-stretched and then stretched method was developed when fabrics for swimsuits were not as stretchy as today.
Initial application of elastic is done.
Next, I folded the elastic over to the inside and sewed with the same zigzag stitch while stretching the elastic evenly.