Thank you Ian i will try it.The concept of development to completion is a myth, development should be the time to achieve D-max with Bromide papers. Over development will affect the tonality and contrast
Sprint themselves actually say: QUICK SILVER Print Developer 30 sec - 3 min (See Exposure & Development)
and although they say 1+9 dilution for paper negatives it would be better to try 1+19, you don't want a high D Max that's almost impossible to contact print through.
Sprint do list 1+19 as an alternative dilution and temperature variations do affect development times although Sprint don't mention it, however their print developers are fairly typical PQ developers nothing out of the ordinary.