If you open up productdetail.ascx located in \desktopmodules\smith.buynow you will see the following style at the top of the page:
div.myTabs {
height:350px;
width:100%;
overflow:scroll;
overflow-x: hidden;
padding-right:7px;
}
Change the height property to something less like 200px or anything that works for you. In the next release 2.93 we have moved this style to the module.css
-Scott