This is somewhat a two part question.

I've got a small 2' tall Dawn Redwoood (Metasequoia glyptostroboides) planted 23' away from a 1' tall Magnolia Macrophylla. I was originally planning on planting another Magnolia Macrophylla another 15' away from the first Magnolia Macrophylla (in the opposite direction of the Metasequoia) so as to have two plants so if one dies I'll still have one left. But then I might end up with two trees way to close, or one tree oddly spaced. The issue I am concerned with is that the trees will be too closely spaced, maybe it would just be better to only plant one magnolia and have more spacing? The other issue is I would then have to move the magnolia, which I also don't want to do.
Just want some other opinions.

All trees swill be planted in a line in order, Metasequoia <-23'-> Magnolia <-15'-> Magnolia

Question 1: Are the redwood and magnolia planted too close?
Question 2: Is it wise to plant two trees fairly close for redundancy?

The Dawn Redwood has the potential to grow to 25 - 30 ft wide and 100 ft tall. The Magnolia will be 30 to 40 ft wide and tall. They're already too close together.

The spacing won't be a problem for another 20 years but I wouldn't add anything in the middle.

Thanks for the response.
From what I see online, Dawn Redwood is 25' wide and Magnolia macrophylla is 20'-40'. So if they grow to the minimum I will be good, but I do think that I should try to give them a little more space. If I move one over a bit I can give it 30ft between the redwood and magnolia. That will give each tree enough room for 30' width.

I had a dawn redwood in my yard in California. It was huge and grew relatively quickly.

You can plant 2 magnolias so you have visual impact in several of years instead of decades.
When the time comes, one will be cut down.
I'm one for planting extras in case some get lost, grow slower than expected or just mature smaller than planned.
There's no law says you can't thin the herd if they all grow like gangbusters.

Trees planted close together, from observation of my trees, and depending on variety, when they get too close to each other will bend branched upward to get away from annoying neighbor.

My Black Pine, already annoyingly has multiple leaders but where it butted-heads with an Arborvitae, it is obvious the branches are heading up, not out.