John,
To answer your questions...
Trailer set up:
1) The keel should rest on a carpeted keel board (2 X 6? , 2 X 8?) that sits inside of, and extends past the metal, horizontal I beam. It's a lot better if the front of the keel strikes something softer than metal when loading or off-loading. Support for an Ensign using a trailer like yours is to have all four pads carry a similar load with the keel also being supported by the keel board. A five point support load is what you're trying to achieve and the keel can carry a bit more of the weight. The pads should be snug but not able to rotate by hand.
2) I do not know to what a v bunk refers. Are you referring to a bow roller at the front?
3) Adjustments to the pads can be done with the boat on the trailer if the jacks are not frozen.
Trailer modifications:
1) Carpeted, vertical guides on either side of the keel board, angled outboard at the rear will make retrieving the boat easier. Having a bow roller at the front will assist greatly in holding the bow at the proper position (fore and aft and athwartship) when retrieving and loading the boat. Make them high enough so that they guide the keel, but not so high that they reach the flaring of the keel into the hull. Building them as high as you can with encountering the flare will assist in guiding the boat in deeper water.
2) Wood with carpet.
3) I can send you pics of my trailer in about a month. It addresses everything you're writing about.
Now... for an important note for you, or for anyone who ramp launches their Ensign...
One of the worst things that can happen when you ramp launch an Ensign is for the trailer tires to roll off the end of the ramp into a hole, suspending the trailer frame on the ramp with the boat not anywhere close to floating.
If you do this, you have screwed the pooch on yours and everyone else's day, and you will have made huge friends with anyone else who is waiting to use the ramp. Your boat and trailer will then be stuck until you can find a way to get your trailer tires back on the ramp (crane? cherry-picker? Stacked rocks? Jacks? I-Beam lever arms?). There is likely no backing the trailer into the water any further and you're certainly not going to get the tires back onto the ramp by trying to drive forward... even in 4FD. You'd have a chance of lifting the trailer if the boat was off, but if the boat can not be floated off the trailer, you have created a nightmare.
When motorboats come to the ramp for loading onto their trailers, they invariably use their motors to assist in loading (drive onto the trailer) and there are ALWAYS washout holes where the ramp ends.
KNOW THE RAMP!
Before ramp launching your boat, explore the ramp fully. Know where it ends and know where any holes exist. Also, know how far your boat will need to be backed in before it will float off the trailer. Know how quickly the water deepens. If the trailer has to be backed a long distance before the boat will float, you might need a long length of cable or chain with one end attached to the trailer tongue and the other to your hitch to float the boat. Chock the trailer tires, disconnect the trailer from the hitch, attach the cable or chain, pull forward a bit, remove the chocks and you're ready to continue backing. Floating the boat and keeping your tires away from the water's edge is advisable. When the boat floats off the trailer and you start to retrieve the trailer, you'll have to steer or guide the trailer to keep it on the ramp. Once the trailer tires are on dry ramp, chock the trailer tires, disconnect the chain or cable, and put the trailer back on the hitch.
It's a process.
Bud Brown