No you don't need the 300-400 CFM I sent you that private message with supplies and things for a smaller version of the ones we use offshore. It will take a little longer but you will have more control and you won't be dredging up any of your hard layers unless you really try to. The PSI is one of those have to play it by ear things. Yes it can go further than 25' How far that I honestly can't tell you since every situation is different. How high of a bank are we talking about and how far across the pond does it have to go.

We made a system once that could literally suck up rocks that were weighing in the 100# range that they had put in and around a platform to combat scour and we were running those up and to a location 40' away. The further you have to move the material across water and land the more Flow you will require.

Hope this clears things up and answers your question some.

Also Check your messages the one I sent you answers a few of these questions and provides external links. So you can get a idea of what I'm thinking will work for you.

Alright sir I have to go get on shift for yet another 12-14 Hour day. If you still have anymore questions I'll check this thread later tonight.