The selftapping screw/bolts supplied are more than enough as far as I know, as long as you make sure the holes you drill are just small enough to give a good bite to the screws. Mine is still as tight and very well attached, has been on over a year now. You do not need to remove the struts this way...
If you do really want to put different nuts and bolts on instead you will prob need to remove the struts as the spring-retaining-top-plate will be in the way.....
Rob