I also use the Tacker and they work better than you think they will. In future however, I do intend to try and do it properly and have the bow roller modified to provide a forward attachment point. Having spoken to a SS fabricator, its not too difficult to modify and add to (but not cheap either!) and I can get access to the existing bolts and nuts that hold it all on via the Anchor locker.
If you look at Yngmar's photo in Posting No. 2, you can see a largish flat and uninterrupted area of stainless steel, forming part of the bow roller assembly, and which is on the port side. You could drill vertically through it and the deck area below, and fit a bolted through eyebolt. You could then attach your turning block to the eye of the eyebolt, and you wouldn't need to pay your stainless steel fabricator anything. Just choose the area for fitting your eyebolt carefully so that you only have one hole to drill. If, as you say, you have access to the nuts that secure your bow roller in place, then by the same token you would also have access to the nut that you use to secure your eyebolt in place, but do use a large "penny" washer on the under side in order to spread the load as much as possible.
No, I haven't done that modification yet, but it's on my to do list for next winter.
