Oh dear...how disappointing!
On a new boat, with keen crew and in your home waters too.
Imho, the SWYTC displacement issue needs addressing. I had similar with my BRE (displacement eventually given as a reasonably realistic 750kg, originally proposed 450kg!)
I have made other posts on this subject.
Avoiding RYA SW YTC is not an option for many of us, especially those based in the SW UK.
BEWARE! The issue is also likely to start affecting others as This newish handicapping system speads, as the scheme is now managed by the RYA and RORC rather than Falmouth based clubs.
While there will always be "bandits" (there is more than one hereabouts, imho) this water ballast "policy" needs addressing if it is not to very negatively affect most Swallow boats.
That said, my new BC 26 also compares badly with the Django 7.7 mentioned above. Neither is water ballasted.
Under white sail, the Djanjo is slower than my BC26 (disproportionate influence of length?), despite being very close in size, weight, and my BC having considerably less upwind sail area (-4.5m2). Both boats have diesel inboards.
The django bilge keel arrangement appears favourable (not difficult when apparently rated like a Westerly Centaur!), while my bulbed fin keel is comparatively heavily rated against, with no apparent allowance for it being a far less efficient lifting keel, rather than fixed?
I think I'll start a new thread?
Ps, I assume you towed to France? How was that experience ferry/admin wise?