I just did this project last week on my 88 TR. I drilled from the outside in, because I was worried about coming out in the raised section below the rub rail and going outside in assured that I wouldn’t. It wasn't very hard to figure out the horizontal position by just eyeballing it and measuring a little just to make sure.
I used Trident 101 as suggested. Found some 1-inch ID on eBay at a good price. I bought 5 feet, but the guy only sent me 55 inches. This is ok though because it still fit. Seems like anything between 50 and 60 would have done the job.
I used a Uniseal and a 45 degree PVC elbow, with about 1.5 inches sticking out either side. I used two hose clamps on either end in opposite directions.
Since I was not sure how it would all fit together, I bought a pack of 1" Uniseals and a pack of 3/4" Uniseals. Then one of each size PVC pipe and elbow. I also had two hole saws, 1-3/4" and 1-1/4". My thru hull was a 1-inch Forespar marelon mushroom head from West Marine.
The hose fit the thru hull no problem, but the hose would not go onto a 1" PVC pipe, so for the tank end, I had to use the smaller Uniseal, elbow, and pipe.
I used a 3/4" PVC plug in the tank where the old vent connected. I then used a 1/2" PVC plug in the end of the old vent hose, with the intention of shortening the hose later and moving the plug closer to the stanchion, rather than trying to remove the stanchion and plug it.
For the gap between the hull and the liner, I did nothing. I debated using thickened epoxy but voted in favor of butyl tape on each side. I can always add epoxy later if necessary.
I had to drill 3 holes. One through the boat, one through the bottom of the shelf, and one through the storage compartment behind the port side settee back cushion.
I also added a SCAD solo tank monitor, which seems pretty handy.
I will attach a few pictures. I didn't really have any issues other than the temperature being 95 degrees in the boat at the time, but I am kind of used to that now, plus cerveza makes it 72 degrees in my head. I can also say with 100% certainty that it has helped with odor so far.