This brooch is far more acceptable.
Firstly, I used a high count dressmakers linen as the base for my embroidery. Not nearly as bulky as an embroidery linen which meant that it gathered better over the base.
I managed to replicate the 'doming' on the front by building up the layers of wadding. I used three sizes and glued them one on top of the other to the base starting with the smallest.
I then glued a piece of the same fabric I used for the embroidery over this.
This meant that there was no glue anywhere near the piece of embroidery but the pale colour of the wadding didn't show through. After this had dried I flexed the card by putting pressure with my fingers on the outside edges. This resulted in the dome becoming a bit more pronounced.
I then gathered the edges of the embroidery and stretched it over this base. Because the linen is thinner there wasn't very much bulk to begin with and I flexed the edges again to pronounce that dome. When it came to sewing the beads onto the edge I fixed them to the very outside edge of the brooch. This helped to accentuate the dome. (A bit of an optical illusion.)
I then sewed the pin in place at the top of the brooch. (Thanks for that tip Queenie.)
I was right in saying the doming of the piece and the size of the pin were the two areas that were the main problems. I think that you could cover your base with wadding and then leave an opening to stuff this with fibre fill or maybe lambs wool. You would have to manipulate it a bit. I will try that way in the future. Repositioning the pin over came that problem without the need to buy a longer pin. This is a far more acceptable result.
The next one is going to be smaller in size.