The Seidelmann 30T staeted life as a MORC rule maxi. It was designed at a time when MORC produced some less than ideal designs and the 30T was certainly one of them. Thier high wetted surface, heavy weight for a 30 foot race boat, low form and ballast stability and small sail area make them a very tricky to sail well at either end of the wind range.
The proportions of the rig on these boats requires quite a large sail inventory to race one competitively.
Build quality wise I am much more familiar with the Seidelmann 25''s and later Seidelmann cruising boats. These were not terribly robustly constructed boats and had a lot of issues with some of the systems (electrical and plumbing) installation.
Unless this boat is very inexpensively priced ($10K or so) and reasonably well maintained, and with a good sail inventory, I would suggest that you steer clear.
In this price range there are a wide range of better sailing, better constructed boats that you might want to consider.