fitting a concertina loft ladder / raising frame

hi guys

so I am a complete woodwork novice and am wondering what needs to be done in order to install my new concertina loft ladder.

the loft hatch opening frame is only 1 and half inches (tall?) and there is a timber backing plate at the end of the ladder which needs to be secured on all 4 corners but the problem is the support plate is 6 inches in heigh so securing the bottom of the plate to the frame is no problem but what do I do about the top?

is it simply a case of add some cut to size 2x4 to extend the side of the frame I need extending or am I miles off!?

any help would be greatly appreciated.

Here are the images of the loft opening and where I wish to install the ladder and a picture of the ladder back plate that needs to be secured onto the hatch frame.

Yes, just build up frame to suit, fix well as you will be pulling ladder away from this fixing under tension.

OK thanks is it just a case of cutting up 2x4 and attaching to that side of the frame and the pictured rafter or do I need to do this for all 4 sides?

The more timber the stronger it will be, running a brace behind the board would also help.