I know Magnum is from a Hallertua descent, so it would stand to reason it would behave like a Nobel hop in late addition. I would think it was closer to an EKG than a Cascade. Some people consider EKG a noble hop.

 

It's a great hop for late addition and even dry-hopping. Flavor is very smooth with spice and a fair amount of fruit. Definitely try it.

 

This is an excellent blonde recipe if you are looking for a good blonde ale recipe.

https://www.homebrewtalk.com/forum/threads/centennial-blonde-simple-4-all-grain-5-10-gall.42841/

 

Wander over to Brulosophy and take a look at their Hop Chronicles. They did some very interesting studies with various hop varietals and perceived aromas and flavor profiles...including magnum. It's very useful information to consider when looking to build a hop profile for your brews. Personally, I've benefited significantly from their work with hops, experiments, techniques, etc and is one of my "go to" resources. Give it a shot.

Regarding magnum, my takeaway from the hop chronicles eval is that the flavor/aroma profile imparted by magnum hops as a late addition are fleeting and not substantive enough for hoppier beer types and it's wise to rely on other hops to work with the magnum characteristics.

 

I made an ordinary bitter with a magnum late addition. It was a little herbal, but mostly clean and pretty floral. It went well with the Maris Otter malt, but I kept the late addition tiny because of the high AA%.

 

High alpha acids contribute primarily to the bitterness, though there is a flavor component, I'm sure. Volatile oils account for most of the aromatic flavors and the aroma properties. Alpha acids are not utilized to a great extent when used late in the boil and won't contribute much to bitterness. The volatile oils aren't boiled off so that they can be a stronger component. Better to use smaller amounts of high alphas at bittering and much larger additions of those hops late in the boil.
I suspect that you'd have gotten much more of the true flavor and aroma of the Magnum hops if you'd used relatively generous late additions.

 

While this is true, I do a very slow chill after the boil (throw it in the fridge overnight), so the alpha acids would continue to isomerize for another half hour or so, and it would have been way out of balance for a tiny beer like that bitter. I see where you're coming from though.

 

Slow chill definitely would make a difference in a beer like an OB...Might be interesting to try a beer like that or maybe a session Blonde with only late addition of some of the higher-alpa hops.