I suspect the rear main, since working with pan is not helping. The in and out of the seals is important. If one is wrong it could really leak bad. I check myself 3 times, looking up confuses me. Also block and cap edges are sharp. When installing seals care must be used to avoid scraping seal sides.
The Felpro seals are 2 piece, so are not offset. Very little sealer used at ends, dry first with q-tip and acetone. For pan, rubber and cork seals installed on dry surfaces, sealer only at corners where rubber meets cork.