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I have a Montauk 17' hull like yours, and use a Continental CV-7 galvanized trailer under it, which fits the boat like it was specially designed for it. You should be able to set yours up similarly if you want to. It looks like you have a good frame design.

As you know, the proper way to set this up is with all weight bearing on the keel rollers. First of all, although you have already spent money for those Yates rollers, I would not use them, as they lack necessary bending strength. They will sag in the middle under hull weight as they are only supported on the shaft at the ends, and the weight is carried in the center.
I would STRONGLY recommend you upgrade to the Stoltz rollers, which have a continuous metal sleeve across the entire 12" width, which transfers the boat load to the roller brackets with no deflection. With Stoltz rollers you MUST use SS roller shafts, well greased, to avoid bonding of roller and shaft. I would also advise the addition of an 8" roller forward, to carry the forward weight of the hull, at the first cross member. It would be easy to bolt one on.

As for stabilizing bunks, all you need are 2 x 4 x 5', mounted on last two cross members.
Anything else is overkill. I simply buy the pre-carpeted ones. Locate them so they fit against the upside down "V" in the hull bottom. This will help automatically guide the boat on to the trailer. Using these smaller, and shorter bunks, will clear up the bottom of the hull for much easier cleaning and maintenance, and less chance for launching damage and wear. I do not like pre-welded bunk brackets since they cannot be adjusted, making it difficult to transfer all weight to the keel rollers. You might want to consider the bolt-on brackets, with SS u-bolts. Pacific Trailer sells these specially sized 1/2" U-bolts.

As for lag bolts, use 3/8" x 2" in 316 SS (important to avoid rusting). Through bolting is not necessary. The 2" length is necessary for maximum holding. Both the carpet thickness, and the necessary washer and lock washer under the bolt head take up the length. You can use an extra washer or two if needed.