A Baby Beehinds bamboo boosted inside the nappy and between the nappy and cover worked fab for my heavy wetting DD1 (when she was still in nappies). If you boost in between the nappy and cover as well as a bit inside the nappy you don't get the leg gape which leads to leaks. And yep, definitely recommend a wool cover as well, had no end of leaks with fleece covers. I used my own hand knit covers as well as the Baby Beehinds wool covers, with hand knits I like an elastic waist to hold everything in better

HTH and good luck