Assuming that the Diverite 7 pound soft weights are running parallel to your spine along each side of the tank on your back, the weight distribution should approximate a 9 pound heavy backplate with a 5 pound heavy STA. There are quite a few people around here using 9 pound backplates with 6 pound weightd STA's which would put you in that approximate range in terms of back mounted weight.
By the way, my approach to the problem would be to use a pair of trim pouches on the top tank band with about 3 or 4 pounds of weight in each one and dispense with the soft weights. There is a possibility that the soft weights may move around depending on the exact mounting method. However, I prefer to avoid custom weights because I travel a lot and do not want to drag lead with me.
As someone above mentioned, we don't know enough about your complete set up to advise in detail. However, some of the other posters are trying to read the worst into the description of your rig. If my assumption is correct, it does not sound convoluted to me. I would have to guess that you are also using a steel tank as you are going to be wearing Michelin man amounts of neoprene for which 20 pounds of weight would only be enough for a very skinny person if an aluminum tank was in play.
As you may have noticed, there are quite a few people around here who are in love with backplates and think that everytning else is a complete piece of junk. Many divers who post in this forum have an agenda and among the backplate users this agenda is unusually strong. Do not get upset with their comments. After all, who are they to you.
I use a Transpac 2 and I am quite happy with it. It is similar to the S-Tec. I also mount weights on my top tank band, but I just thread the tank band throught the weights. Its effective, and uses standard weights that are on every dive boat.
As for those of you whou have some unused gear in your closet that you hate. Please PM me and I will provide an address where you can ship it to. You may rest assured that it will be put to good use.