In both install2.php and install1-1.php, an attempt is made to get collation right for UTF8 forums.
But in each of those cases, the collation is GENERAL (utf8_general_ci).
But not all SMF forums use general collation. Many forum owners prefer collation that better suits the primary language of their forum.
Is there some way to find out which collation is being used, for example, in the smf_members table, and use that for the columns on the simpleportal tables?
Please see an example of this problem at:
http://simpleportal.net/index.php?topic=10311.0

! Make sure installation completely relies on SMF functions for collation.

Commit: 08a3085e8cd419d6d3b14c3ed653df725e44c051

If I understand the issue correctly, you need to adjust SP table collations in the installer to reflect what the rest of the SMF table installation is set to.
Is this correct?

Why not just create a small routine at the bottom end of the SP installer & use 1 of the main SMF tables as a reference?

ie.
function SP_set_collations()
{
global $smcFunc;
$sp_tables = array('sp_articles', 'sp_blocks', 'sp_categories', 'sp_functions', 'sp_pages', 'sp_parameters', 'sp_shoutboxes', 'sp_shouts');

$result = $smcFunc['db_query']('', "SHOW FULL COLUMNS FROM {db_prefix}settings");
while ($val = $smcFunc['db_fetch_assoc']($result))
$collation = $val['Collation'];

$smcFunc['db_free_result']($result);

foreach ($sp_tables as $sp_table)
$alterTable = $smcFunc['db_query']('', "ALTER TABLE {db_prefix}{$sp_table} COLLATE {$collation}");
}

SP_set_collations();

.. or let people with the issue just put the above in a php block & preview it.