Hi Sam,
OK - I'll start off with data from my Savvy S (from memory).
Empty weight about 310 kg - I have long range tanks, dual brakes, centre stick, adjustable seats, transponder, Garmin Aera 500, manual flaps, electric trim....
I usually fly solo, and I weigh about 60kg. With full tanks, and about 7kg of stuff in the baggage my take-off weight is around 470-480 kg.
So my figures when solo are usually closer to the old 450kg ones in the POH rather than the 600kg ones.
The stall speed gets hard to measure when I fly straight and just slow up as the angle of the pitot is high and not really reading accurately, but with full flap I see it around 25 kts. When clean it is around 30kts, but same issue with pitot at high AoA. (Book figures for 600kg are 30kts and 35kts respectively).
I cruise at around 4800-5000 rpm (100hp ULS), and my speed is around 82-83 IAS. I flight plan on 90 kts TAS, with cruise altitude usually over 4000ft AMSL, and over 3 years I have found that to be largely accurate.
I get about 15 litres per hour with 98 octane MOGAS (POH figure is 18.5). This gives me an endurance of 8 hours + reserve, which is well past my bladder endurance...
I haven't really measured my take-off roll as it varies with wind, surface, etc - but it would usually be less than 200m, and my rate of climb solo is usually 800-1000fpm as the flap extension speed is 60kts so I have to keep the nose angle high enough to avoid exceeding this. I usually climb out at 55kts, and I am frequently at circuit height before turning crosswind.
Landing distance is also usually less than 200m or so - I do not try to land short most of the time as it puts stress on the u/c to do this, and as my home field has 1200m of runway I really don't have to! Much shorter landings are definitely possible. Just search Youtube for videos of Savannahs doing short landings - there are many!
BTW - see if you can get Revision 6 or later of the POH as that has figures for both 450kg and 600kg MTOW.
I hope this helps. I have certainly been happy with my Savannah since I bought it, and there are many Savannah owners/builders in Australia who I think feel the same way.
Let me know if there are any other figures you would like, and I will try to supply them from my experience.
Good luck with convincing your family!!
Regards,
Neil