My barely novice (and I use the word "novice" very loosely) opinion would be to avoid the shelf all together. Get as deep as you can as quickly as you can within reason. Your kidney shaped pond will have enough perimeter shallows for plant growth the way it is. And, if you get that clear water you suspect, the shelf will eventually fill with vegetation.
I guess it really depends on your goals for the pond, now that I think about it. I like bank fishing and 15 to 20 foot of potential snags and weeds does not sound all that fun. But, boat fishing is a different story...there, I rather like the vegetation near the banks and it's not as bad to deal with.
What's your goals and reasons for the shelf?
Welcome to the forums Tony!
