At this point, the only way to deal with this is to use the spandex sleeves and retainer band to assist securing behind the glans to maintain extension. You should probably go a size smaller to offset the silicone expansion on your next order.
A tip to eliminate the stretching that occurs during insertion of the two fingers and thumb down the sheath, is to first put one of the spandex sleeves over the glans and alway down the penis shaft. Then fold the base section of the inner wear sheath so that you can easily thread the excess spandex sleeve that hangs off the penis thru the sheath and out the other side past the silicone ring. Slide the bas of the folded sheath over the glans and unfold the edge partially down the shaft. Then slide the sheath into position at the base while pulling the spandex sleeve off to remove. This will effectively eliminate the excessive stretch that occurs with the finger insertion technique.