Does the A-frame by itself provide sufficient lateral stability to keep the mast from wobbling off to either side, or do you also require some extra support like baby-stays to the mast?
I don't know what the mast step on your boat is like, on a CM26 the step has a slot so the foot of the mast has a little vertical movement allowable, see picture 6 of Mike's photos. Also, on the CM26, besides the forstay and aft stay, there are side stays (mast head to spreader bar to chain plate) and forward and aft side stays, (what you refer to as baby stays).
Step by step;
1. The base of the mast is placed in the mast step and the retaining bolt is inserted, but left loose.
2. The aft stay, side stays, and aft baby stays are all attached to their respective chain plates.
3. The bolts on the bottom of the A frame go into the chain plates for the forward baby stay.
4. Both of the forward baby stays are attached to the eye bolt at the top of the A frame.
5. The main sheet runs from the top of the A frame to the forward chain plate.
In this position the tension on the side stays is almost the same as when the mast is fully erect. As the mast comes up the side stays will prevent any excessive side sway.
Once the mast is up, attach and tighten the forstay, then disconnect the forward baby stays from the A frame, remove the A frame from the forward chain plates, and connect the forward baby stays to their respective chain plates. Tighten the bolt that holds the base of the mast, adding and tightening a locking nut. Of course, once everything is in place you would want to check the tension on all the stays.
Coming down is simply reversing the process. Always remember to connect the forward baby stays to the a frame before removing the forstay from it's chain plate. Yes, I made that mistake once, and only once. It makes things rather difficult.
I hope this helps.
Penny