Scabbing ceiling joists

Landplanner1

I've got a 1902 home that has severe powder-post borer damage and dry rot in 2nd floor ceiling joists (attic / no living space above). [Lath and plaster now removed to facilitate repairs]. Existing joists are 2"x6"x16' @ 24" O.C. The roof/Facia/soffit framing for the house is odd and has extra space which allows easily working in new (2"x10"x16') joists and for sistering beside the old ones that are not so badly damaged. Clear span is 15.25'. [The bugs are LONG gone, but I'm spraying everything with Timbor anyway].
However, there is one place where the pocket is too shallow and I cannot get the new joist into the space onto the top-plate. I am inclined to cut two feet off of a new 16 footer (2x10) then scab a second new 10 footer beside it (with the 2' piece scabbed back in line with the cut-off to make dry wall installation easier). I am inclined to use a heavy pattern of 3" #10 deck screws to put them together. [I figure that any glue that might be suggested will simply be high tech powder in another 100 years] Does this seem adequate? Would this pass code anywhere?

* Answer to query (why one won't fit): Small Gable on front of house changes framing to eliminate pocket, cutting top of joist at angle won't do it.

joecaption

Trying to guess why one of them will not fit. Is it because the roofs in the way? If so then just cut the top of the joist at an angle.
I would use constrution adhesive when you sister them.
Screws are fine, but if you really want them to draw the two pieces together predill the new wood with a bit that's just slighty smaller the the screws major diam. If you also isert the screws before lifing it in place you not have to be standing on a step ladder fumbing around for screws.