You can get rid of the side, bottom and top handles by creating a file called
userstyle.css with the following content:
#userstyle.css
div#overlay #egrip, #ngrip, #sgrip, #wgrip {
visibility: hidden;
}
Place it in the conf directory. The corner handles are: #negrip, #segrip, #nwgrip, and #swgrip. Any of those that you don't want you can add to the list.