Skagits are an acquired taste to someone who knows only fishing with conventional lines. You need to adopt a totally fresh approach both from the points of view of matching a skagit line to suit your own rod and casting style.
For example , I quote from my previous post,
"Use mine with a Gaelforce Patriot 600 grain which is just bang on for me.
Depending on your style though you may want the 650 grain which is more in line with the recommended window."
What suits me will in all probability, not suit you.
The 13ft 7in Atlas has a window of 38-42 grams.
The 14ft 9in Atas has a window of 40-44 grams.
That does not mean to say that you would be comfortable with a 42 gram head on both as your style may suit a lighter end head. An experienced hand would happily pick up lines way outwith these guidelines (because that's only what they are) and throw them a mile with both rods. What's sauce for the goose and all that.
So, what you really need to understand is, get a line that suits you, not one that the manufacturers tell you you need. Try before you buy.
I don't know how far you are from Kilkenny but my good pal kgm has a load of Gaelforce heads and a day down the Nore might stand you in good stead.
I spoke to Scott when I bought the rods and asked him his recommendation on skagit weights and he replied, quite honestly, "I don't know Tom, just whatever suits you."
If you want to bamboozle yourself even more a wee look at Bob Meiser's website will help you either to understand the grain window theory or to blow your head clean away.
R. B. Meiser Fly Rods - What Is A Grain Window?
Essential bedtime reading.