Shower tray needs to be moved away from wall to accommodate waste.

[Jomatiling]

I’ve had to move shower tray about 50mm away from the wall so that the waste is not over a joist, what can I do to bridge the gap?
I was thinking to fill it with Wedi board and the tile over it? Any suggestions?
Thanks

 

[al strachan]

board it out floor to ceiling would be my choice if it's feasible. Any steps or ledges down by the tray will be a nightmare regardless of how well its done.

just my tuppence and a free bump