I fitted a Sleipner 100 kgf retractable thruster to our DF 44 (2006) last winter and it has been fantastic. The work of cutting a large square hole in the hull and laminating the unit is NOT for the faint-hearted but saved me thousands of Euros compared to a range of professional quotes. It took me four weeks of more or less continuous work and another three fitting batteries, cables etc. and then rebuilding the forward bed. The water tank in the bow could stay but sail storage has been sacrificed. The unit is very quiet and powerful but you always have to be aware of the danger of catching loose mooring ropes when the underwater hatch is open. We could not fit a tunnel due to the shallow draught forward of the 44. We did consider a jet but decided against it because of the weight of the unit and power requirement of the motor. Hope this helps – I have photos and more information if you need it.