Hi Guys
@ajperry I would drill through the wall carefully noting when you lose resistance as this will give you an idea where the cavity begins (make sure you don't end up drilling through to the interior) then stop the drill and push it in till you hit the interior wall, the difference between the two will be the space you have in the cavity it will also tell you how long a thread you will need and that is the width of the outer wall plus the length of the spring toggle when closed plus the depth of the bracket plus about 10mm to make sure you can get the toggle to open. The reason I suggest sleeving the screw is due to the movement, the thread will be considerably thinner than the hole and it would be advisable to reduce the opportunity for the thread to flex around in the hole, might I suggest offcuts of plastic plugs but that is just a thought. Once you know the length of thread needed, you will need to buy replacement screws for the ones that came with the toggles (you may be able to buy toggles with shorter screws to save cost but don't do so at the cost of thread diameter),
@MitchellMc , There are specific fixings for dynamic loads and most people don't realise this. In a previous life (back in the UK I worked for a company called Spit fixings (Special Products For Industrial Techniques) who were a french owned competitor to Hilti, I was in sales and also had such jobs as teaching customers how to use explosive power tools safely (the reason I eventually left the job as a customer who was trained by a colleague had an accident and he was blamed, I didn't want the same thing happening to me!) Anyway, I digress. Usually the dynamic load anchors are self drill anchors and in setting these anchors they create a cone shaped hole with the base of the cone on the inside. It is this cone shape that makes it capable of taking dynamic loads as other anchors which are inserted into a straight sided hole rely on outward pressure and they will "walk" out of the hole. And then there are chemical anchors!
