I may be totally off, or using the wrong verbiage... but to me, hull speed is the fastest you will get your boat to go before you plane; however, it is possible to go faster than your hull speed- but I've never seen it done with trolling motors.
Hull speed (I think, I'm going back to college now..) is more of a drag on the hull than it is an actual speed. It has something to do with displacement of the water creating wave drag (I think it's how fast your boat can displace water, and how the wave action of the water creates drag as it goes under and down the sides of your boat). Hence why bass boats only have a few inches of water under the transom and motor at WOT.
I think if I remember correctly, to figure out the hull speed of your boat, take the square root of the waterline length (length of boat that is at the meeting point of water and boat while floating) and multiply it by 1.3 or 1.4 (I honestly can't remember).. I think I determined my 18' hull speed is around 5.3-5.4. It will go faster without planing I'm sure, but there are too many variables to account for such as: 1 - adding more batteries for more trolling motors and 2 - drag created by each additional trolling motor. That's why the bigger 48-72v motors are better... you have more batteries, but you also have a lot more thrust/prop spin with a constant 60v as opposed to a 105# trolling motor running on 36v. I have ran my Xpress (71# bow TM, 2 - 80# transom TM) against guys who had 48v motors, and I thought they would leave me sitting... but I stayed right with them for about 10 minutes, then they started to walk a way a little bit, but only by a boat length or so. Now if you get one of those Ray electric motors - you'll plane and won't need to worry about hull speed!
Kayaks are really the only things I've ever seen that can go faster than their hull speed without planing - but that's what they are designed to do.
If I missed your question on hull speed, let me know. I should have probably researched this a little more before I wrote all that, so I could be totally off.