Since you've already glassed the exterior and may not have put on the gunwales yet . . . what about slicing the stem right down the middle (with a dozuki or somewhat similar thin saw) and unfolding the whole front of the canoe by a few inches or more at the top to give you that whole bunch more access you need as if just a regular canoe.

Then glass the interior on both sides and then glue the stem back together. Maybe cover the stem with 1" width of glass to keep one happy.

The only tiny problem is the slight cutline down the ctr of the stem - If a good job is done, probably won't see it; if not and if it's laminated, add (or remove/add) another lamination to hide the jt.