Okay, this an endless problem for my son's chair. He has a Boing and there are only two brake types available, the scissors and a rather large lever type. Neither will hold his chair in place. The old type brake they had worked but his dad had to modify them by making an extension for them to stay out of the way and still reach, holding it is place well...and within six months the bolt holes have worn out.
The suggestion was made through Colours to try a type of brake used for inclines, from the following website: http://www.edmond-wheelchair.com/grade_aids.htm

Does anyone have any experience/knowledge of these type brakes or any suggestions again?

I think my son is active enough in and out of his chair constantly that he is just plain old wearing it out in one way or another every six months or so, thus he needs a braking system out of the way and strong enough to not need this constant readjustment, replacement.