Quick question: slow roast lamb - how long for small half shoulder?

[Trumporange]

I plan to slow roast a 750g boneless half shoulder of lamb, in foil for the first part but last time I did this I followed a recipe for a larger joint and it was a bit dry.

How long for a half shoulder this size - I want it tender (pulled style) but moist!

The last one I did (with bone) suggested 40 mins per 500g plus 40 mins.

Admittedly for a bigger joint - 1.5kg - I put it in a hot oven for 30 minutes then 120 degrees for 8 or 9 hours. Had it last night and it was absolutely gorgeous - very moist and cut-with-a-fork tender.

Thank you all - much appreciated.