Question - Roof Structure - Replacing Roof Struts

I need to replace some 4" x 2" timber struts that fit between the purlins and a length of horizontal timber resting on top of a load bearing wall.
The top of the strut (the end that the purlin sits on) are cut to an angled 'L' shape to accomodate the purlins. The side of of the 'L' nearest to the roof tiles is cut long enough so the whole height of the purlin is seated on the strut.However, the bottom of the 'L' shape is only long enough to enable about a one and half inchs of the purlins width to sit on the strut. This leaves a substancial amount of the purlins width sticking out into free air.
Is this ok or should I ensure that more of the purlins width is supported by using 6"x2" or even 8"x2" timber so that a longer cut can be made in the strut and thereby more of the purlins width can sit on the strut ?
The bottom of the struts are cut straight (no 'L' shape or notches etc) and nailed into timber sitting on a load bearing wall.
Is it OK for these ends of the strut to becut straight or should they be notched to an 'L' shape to give a more rigid fitting on the horizontal timber that is sitting on the load bearing wall ?
I also noticed that some struts coming from one side of the roof are *exactly* opposite struts comeing from the other side of the roof structure (ie, the ends of each opposite strut butt-up face to face against each other where they sit on the horizontal timber on the load bearing wall).
However, there are also some cases where opposite struts are fitted differently to this, and are positioned so that the strut ends are side by side to each other (ie the left side face one strut is against the right side face of the opposite strut.
Which of those two methods for opposite struts is the better or approved method ?
Many thanks for any help or suggestions.
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