So how should I take this situation: we have a new dog, ex-RSPCA, nearly two years old, now in the habit of sneaking into the bedroom to piss or shat on my Harley magazines (Heavy Duty).

Must be some scent on them attracting him, what have you been doing over them? Must have been some exciting articles and pictures. 

Have you read HD mate? Big blokes with long beards don't do much for me.

Try wiping them with a weak solution of Citronella oil, they don't like the smell, works on car, bike tyres etc as well.

Could be a nervous thing if it is new to the household.

It's one of those 'intelligent' dogs that can open a sliding door, normal door (if can be pushed), and a wire gate. Shat in a pair of slippers the other day too. Outstanding aim really. Understanding now why he ended up at the RSPCA. 

That smart could show boredom and depending on previous owner attention seeking, could try toys or a kong full of food plus regular toilet visits outside like every hour for a while. All about retraining. 

Leave your spank mags out, see what the results are then ? or the political weekly with Turnbull or Shorten on the cover, this should determine more about you dogs intelligence ?

Have you tried using his kennel as your toilet? Might teach him that way 

To be serious, it is not hard to house train any dog with patience and treats, but perseverance is the key. I have four dogs and all are rescues or hand-me-downs. No issues here.

My rescue dog, is house trained, but has an abandonment issue. Has to follow me 1 inch behind, and pines if go out without him, but would never think about shitting on my motorcycle stuff, err that's me, not him.ha.

Are you sure it's not a jealous missus?

Thanks for most of the comments. Yep, training has begun and my mags are now up higher. Up to me to teach this young'n where to do his business.

There is a good citronella spray you can buy that works a treat. I found it worked well on the compost bin to stop our dog as a pup trying to raid it. As our ol fella aged he became a bit more of an inside dog and took to climbing on the lounge as soon as we weren't looking. Got an old cushion and sprayed it with the citronella and bingo hasn't done it in years. Hint. Be a bit carefull what you spray it on. 

Have you considered rolling up one of those magazines and introducing it to the other end of the dog