Best method for floating bookshelf, 2x4 skeleton or iron-rod brackets

[BennyK]

If I want to make a floating bookshelf around 7-8 feet long (i.e., has to carry a real heavy load), what would be the best method between these two ...


1) 2x4 skeleton and put plywood or plank box over:

2) Buy iron rod brackets:

https://shelfology.com/shelf-hardware/aksel-md-floating-shelf-brackets/

I'm looking to make a shelf around 7 to 8 feet long and about 12" deep.

I may have to give up the idea of a floating shelf and just use L brackets, but I wanted to get opinions first. Do you think either of these methods would work? Which would be stronger? Is there a risk of the 2x4 skeleton drooping over time?

I should add that I am fixing to a plasterboard wall with wood studs spaced at 60cm/~24" apart.

 

[SFK]

Also these.
Note the bar that goes into wall to give more strength.
But needs to be a solid wall behind.
SFK


https://www.ebay.co.uk/itm/Floating...rand=Unbranded&_trksid=p2047675.c101195.m1851

 

[^woody^]

I made one 2500 x 450, well it is actually a raised floating hearth, using CLS 38x63.

I used two 100mm angle brackets per timber to make the frame, as I was not confident that screwing in to the endgrain would suffice. The frame was then resin fixed to the wall, but I suspect that if screwing into timber studs a good enough fixing can be made - probably a couple of nr6 coach screws with washers per stud.