As I understand it - I would set the front so the LCA is as flat as I could get it then adjust the rear so there is some rake. Perhaps the same proportion as derived from the manual. The front is the most critical. The flatter you can run the front LCA the better you can control the camber which is critical to keeping the largest contact patch against the road surface when cornering.
As the roll center drops, roll is increased (longer moment between RC and CG - effectively softens springs). As roll increases, the camber on the unladen tire will move more positive (lower pivot moves up, hub falls, top of tire tips out, contact patch is reduced.).
If you raise the LCA (pivot) jacking is increased on the unladen wheel because lateral weight is transferred thru the suspension components (un-sprung weight) acting thru the roll center. This gives a component of force acting horizontal at the contact patch and another acting vertical (height to RC). As the roll center is raised the vertical component of force is increased. The higher we raise it the more weight is transferred from the unladen to the laden thus giving up much needed traction on the unladen side while over loading the laden side. As the unladen tire is raised further traction on that side will be reduced as the tire is scrubbed across the traction surface (what happens when it rolls back?
).
As I remember, the front RC of mine with Avons is around 1.5" off of the ground with the arms flat. I fitted mine with extended ball joints to get the arms flat and with the taller tire I sit 4 7/8 at the front. Interestingly with the rear at 5 1/8 this puts the half shafts nearly horizontal.
Make it look like you want - Crawl under it and check the angles of the front LCA - where are you? Photograph it.
Adjust front LCA flat - step back and look at it - where are you? Photograph it.
From what I have learned working with mine, I would not be concerned with ride height until I did these two checks.
Race cars run flat arms because it is the most neutral compromise. Is it possible it will run faster above or below - sure - but without testing or simulation I would not bet on it.
Check out the geometry on modern GT or Open Wheel cars - RC near or at the ground and CG as low as they can get it to shorten the roll moment. They do not raise the RC to shorten the roll moment - they lower the CG. By placing the RC at the ground they are able to greatly control jacking. The LCA is still horizontal (the more things change the more they stay the same).
It needs to look correct, but Form should follow Function - the devil is in the details. Not sure how much it matters (within reason) unless you plan to run to limit.
Let your conscience be your guide.
chr