Grassroots DockSports: wwGRMd? Need help!

I need to replace 2 rotten old boat docks at my house.  Through a friend of a friend, I've secured a ton of 6'x8' Pre-fab Dock 'segments' from someone who has way too much money and ripped them out after 1 year and replaced with aluminum.  It was the right price and they're virtually brand new, but I need help on how to affix them securely, bulletproof-ly, and for long-term. 

These are permanent docks- we do not need to remove them seasonally.  One end of each dock is anchored on land, and the deepest segment is about 5' water depth.  Each are going to be 24' long total.  Some segments will need to be secured length-wise, and at the end of each dock I will be sandwiching 2 deck sections together for a 12'x8' platform.  They are all sturdy 2x6 PT built, 16" on center.  My initial thought was to get a bunch of 1/8" steel plates, say 24"x 5" made up to sister the exposed end connections of each segment (for a 12" overlap on each dock segment), and then just lag bolt 16" between the 'segments' underneath between the joists with smaller 4"x 4" plates as washers.  Do you think that's sturdy enough?  I plan to run support runners to cement tubes buried into the ground every 8' fwiw.  

I am not interested in floating/partitioned dock setups, which was how they were mounted prior.  Been there, done that, hated them.  Too much boat damage and noise. 

Please let me know if I'm on the right track! 

Thanks in advance! 

In reply to golfduke :

I have long term experience with docks on a lake north of where you're located.  If you don't have to worry about seasonal ice movement damaging the docks, timber cribs filled with rocks under the dock sections are about the best long term at the water depth you're describing.  If you locate the crib or cribs properly, they would support most of the weight from below so joining sections as you mention above would be fine.  If you can't do cribs, galvanized pipe supports work OK but will need a level of annual maintenance to keep things leveled up.   Know that NHDES is much more aware of shoreline / docks and so on these days so be sure to do your research.   It sounds like you're replacing existing so in that case you should be grandfathered.

Got any pictures?

Photos would help a bunch.

I'll grab some pics over the weekend, thanks guys!  The lake is dam controlled and drawn down 5' seasonally, so ice floes are not a concern.  
 

 I also have nhdes permits for all of this, including a shorelands impact study.   I have too many seasonal nosy neighbors to do it any other way than by the book, haha.  But I appreciate you looking out! 

I don't have many answers but I always have an opinion.