I like this!! That is what usually users afraid of- to check whether their LNBs located in antenna's focus and aiming to right spot on surface of the dish.
Download Parabola Calculator, measure your dish and insert data in the program. You will get precise position of focus. Put LNB to that position and you are set.
Feedarms and LNB holder could be made fully adjustable, not a big deal.
When you know position of Focus and opening angle of antenna (this angle can be measured as well), than bisektrise of this angle will be tilt angle of your LNB, I mean green line on my picture.
If member does not know exact antenna model and wants to somehow adjust LNB and get some signals, I would say that is mission impossible. Anyway, he will need to fix LNB in focus, my picture was only an example. Feedarms could be made even out of wood with LNB glued, but it has to be in focus anyway.
Much easier than is to call installer and ask for solution or buy new dish and install it.