Well after a number of trips away we've bitten the bullet and bought a tender. Fortunate to pick up a Zodiac and Mercury 2.5HP from an ex-colleague at a good price.
Spent the weekend at Tangalooma and gave it a go for the first time. Great. We've been struggling with a $100 "toy" boat for a while now (Gunter has a video of Margaret unsuccessfully trying to board that one!) but this adds a new dimension to our boating.
Best thing is the whole deal will fit (if carefully packed) in the Investigator cockpit locker, oars, bits & pieces included. The Zodiac is a little bigger than ideal for the Investigator at 2.6m, but it will carry more and hey, a good deal is a good deal. The Investigator continues to exceed my expectations and being able to fit a tender+ OB in the cockpit locker is just another example.
I also considered a nesting dinghy, and if anyone is interested Ian Kirk (Sherlock) has sent me drawings and a scale model of one he had designed to fit on the foredeck of an Investigator. Happy to pass the details along. I'm sure Ian won't mind.
Attached a few pics.