Not sure if you have seen this before, but Powerbase from DCC concepts claims to help with gradients of 1:30 and more.

DCCconcepts PowerBase

it looks like a more expensive version of the hornby magnadesion,ie-magnets in the loco for rail grip,I just add lead shot to the smokebox  gives the same result
:thumbs;-):cool:

You can get thin magnetic strip with a self adhesive backing that comes with fly screen kits for windows and doors, I wonder if that under the rail with a small neodymium magnet under the loco would give the same result.