I'd actually prefer the Scout configuration with a fixed internal magazine, I dislike having a bulky detachable sticking out at the balance point. That 5-rounder's not too bad.
And I've got leather to carry spare rounds, but seriously doubt I'd ever carry extra mags.
The metal bottom wouldn't reduce weight any, but it'd be more resistant to aging, cold weather, and impact.
I just don't like plastic down there, even if it shaves a couple ounces.
I've not yet seen the fiberglass stock, but I'm kinda liking the laminated wood. I've got it on my Guide Gun.
If the synthetic is fairly solid, I could live with it, but I also dislike thin hollow & flimsy synthetic stocks.