My comments would be to look at the critical gain analysis to make gain adjustments and to be cautious of the custom ear molds as from my experience they do not necessarily fit as well as properly fitted domes or sleeves. Especially if you have small or twisted ear canals.
My mother has KS8 hearing aids with moderate to severe hearing loss. Her right ear is worse than the left. She has small ear canals that are also at an odd angle. She started with closed domes, but those would not stay in place. Went to closed click sleeves and still experienced problems with feedback and getting them in correctly. Next she tried custom ear molds which she and I were very disappointed with. They were large blocky and really only sat in the outer ear. They did not really fit in the ear canal. They were not what I thought would be custom. They were the worst of the worse as they kept falling out. She went back to the click sleeves while they sent them out to make new ones. She still experienced feedback, but learned to better insert them. When we went back to try the new custom which were really no different than the first ones. The tech ran a critical gain analysis and based upon that reduced the gain in the pinch point areas. With the gain adjustment and practice at putting them in and finally understanding that she has to check the click sleeve alignment she is very happy with them. We returned the custom ear pieces for full refund. She still has to watch the insertion and sometimes make an adjustment to get them to work.