Best way to do this is a topic of some debate on here (along with most things tbh) and I think you'd have had more action on this thread if you were posting 'in season'.
You very seldom, in my experience, see anyone towing with a transom saver type device in the UK. What you see more often is what might be characterised as a 'ram saver'. That is something which is designed to prevent the tilt ram from having to take the strain of supporting the engine while towing. Generally it'll be a block of wood jammed between the engine and the yoke to take the weight of the engine. I certainly found this a necessary with my old 20 year old Yam 2 stroke because the ram would gradually let the engine done while towing of i didn't chock it up with something. With my new rig I've towed it for a season without a chock with no noticeable ill effects, but this season i have made provision to chock it up.
There is a school of thought that says a transom saver which attaches to the trailer doesn't really do you any good as there's a certain amount of flex between the boat and the trailer and you don't want that flex transmitted to the ram or the transom. Others will say that the boat should be strapped down tight so that this isn't an issue.
What I think you'll find most people agree on is that:
a) the tilt lock isn't up to the job and probably holds the engine at too high an angle
b) you should probably have the engine at and angle less than 45 deg from vertical.
Sorry, no concrete answers but some more to think about.