I was a bit annoyed of not beeing able to attach them, too. So I edited the config. Just open the part.cfg in *\Parts\fuelTank\ with notepad and add node_attach = 0.0, 0.0, -5, 0.0, 0.0, 1.0, 1 under node definitions and change the attachment rules to attachRules = 1,1,1,1,0 Hope that helps