I don't doubt that ramminjammin hit 21 knots OVER THE GROUND, he gave the impression that he sailed that fast. In B.C. there are several places such as Seymour Narrows where the currents can reach 14 knots and this is possible to achieve. Hardly an accurate description of the Tartan 30's capabilities though. Based on my looking at Tartans from that era I think they are a good solid boat that of course has the same issues any 25 year old fibreglass boat does- leaking chainplates, soft deck possibly. and outdated equipment. It usually comes down to price and how capable and willing the prospective owner is at repairs.
Currently refitting a CS27