Can mutt show the index and body of emails in a horizontal split?

Question

I'd like to have mutt show an index of emails at the same time as the body of the selected email, horizontally next to each other. I understand that you can set mutt up to show the index of emails at the same time as the body of a message itself in a vertical split. For example, in muttrc:

set pager_index_lines   = 10    # number of index lines to show
set pager_context       = 3     # number of context lines to show

This produces a pane showing the email index at the top of the screen, with the body of the selected message in a pane below.

  62 r   Jul 22 Sender 1        (783K) Subject 1
  63     Sep 03 Sender 2        (2.9K) Subject 2
  64 r   Sep 17 Sender 3        (2.0K) Subject 3
  65 r   Sep 17 Sender 4        (4.9K) Subject 4
  66 r   Sep 18 Sender 5        (835K) Subject 5
  67     Sep 21 Sender 6        (2.3K) Subject 6
  68     Sep 21 Sender 7        (136K) Subject 7
  69     Sep 24 Sender 8        ( 37K) Subject 8
  70 r   Sep 26 Sender 9        (3.8K) Subject 9
───────────────────[ 71 messages ]───────────────────────────────────────────────────────
Date: Thu, 17 Sep 2015 09:19:22 +0000
From: Sender 3 <foo@bar.com>
To: Me <foo@bar2.com>
Subject: Subject 3
user-agent: foo/bar

Body here. Luctus inceptos tortor parturient bibendum diam. Posuere diam, pharetra
purus nibh posuere, mi feugiat arcu, ve. Dis nostra inceptos, urna, et habitasse a
purus in est ante. Nisi eni lorem. Nonummy non. Leo, dictum venenatis. Mollis.
Dignissim est. Potenti diam et convallis proin aptent ipsum adipiscing dapibus.

Is it possible to have the panes horizontally next to each other instead? i.e. as below

62 r   Jul 22 Sender 1   (783K) Subject 1 | Date: Thu, 17 Sep 2015 09:19:22 +0000
63     Sep 03 Sender 2   (2.9K) Subject 2 | From: Sender 3 <foo@bar.com>
64 r   Sep 17 Sender 3   (2.0K) Subject 3 | To: Me <foo@bar2.com>
65 r   Sep 17 Sender 4   (4.9K) Subject 4 | Subject: Subject 3
66 r   Sep 18 Sender 5   (835K) Subject 5 | user-agent: foo/bar
67     Sep 21 Sender 6   (2.3K) Subject 6 |
68     Sep 21 Sender 7   (136K) Subject 7 | Body here. Luctus inceptos tortor parturient bibendum diam. Posuere diam, pharetra
69     Sep 24 Sender 8   ( 37K) Subject 8 | purus nibh posuere, mi feugiat arcu, ve. Dis nostra inceptos, urna, et habitasse a
70 r   Sep 26 Sender 9   (3.8K) Subject 9 | purus in est ante. Nisi eni lorem. Nonummy non. Leo, dictum venenatis. Mollis.

Answer 1

No, mutt itself cannot do this and no patches currently exist for that, either.