Hope it's okay to chime in, just thought i'd point out that if you want a handguard with flat sides and bottom that has the arca rail integrared into the bottom, you might want to give our (Catalyst Arms) Fast Track a look. Because the rail is integrated it runs the full length which is nice. The products being referenced above are great stuff as well though. Definitely a buyer's market!
Catalyst Arms Shop — Catalyst Arms
www.catalystarms.com
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You should make one of those that’s fits this Seekins upper: