Stuart Anderson has recently resurrected his blog called patternschool.online which focuses on pattern making for stretch fabrics, specifically dealing with swimwear.
He goes into great detail regarding how to use stretch properly, tension lines, etc, and offers a series of blocks and manipulations of the blocks to achieve different styles.
He also sell his basic blocks on the website.
It is a treasure trove of technical information freely shared. Well worth delving into!
There is a facebook discussion group as well for those who do FB