Tel, sounds like your getting into this big time.
I played lap steel many many years ago, matter of fact it was a lap that took me from guitar through to playing pedal steel. Cant remember much about it now, purchased it from a music shop in Brum, black, 6 strings, I know I used to tune it-
E A E A C# E (thats what it told me on the wrapper) as I did my dobro in later years. It gave a fairly reasonable hula sound, and enabled me to get to grips with the bar and picks, although I was using thumb and finger picks on guitar,so that was not so difficult.
I fairly quickly went for a bargain, second hand pedal steel and never have gone back to a plank.
I have only recently been thinking of making one purely as a project, Im sure there are lots of guys out there that have done it, or are in the process like yourself. I found a few plans and build details on different websites, all looks challenging but would imagine-good fun.
Now retired (semi) Ive recently finished my workshop (only taken 10 years

) looking at the info found, I think I have enough basic woodworking and engineering skills to knock something together, how it would sound though?
It will be interesting to follow your progress and be sure to let us hear the final sound.
Best of luck with it,
Dave.