Done away with screw in bungs,too tight crack ring

 A good quality ) ring, and dont screw the thing up to death.. finger tight and 1/4 turn.. no jamb , no broken ) rings.. Which is why I put in and dont let crew do so...

Theoretically pressure from the outside would help seal but in reality how much pressure is there and if your seals are going to leak, they will leak. Hmmm

 Nope.. it is a thread.. and any 'end pressure will not close the 'gap'

One would be amazed just how much water pressure there is under the hull... say the keel is 150 or 200mm under the water. Now get a bucket water, turn a mt glass upside down, and push it down that deep..

Bit like my hull leaks,well fill with water and see where??Funny thing is water doesnt come out due to the pressure on hull maybe sealing it

 I will lay odds, if it is not the bung or how the bung insert is sealed in the bottom of the transom...
 I have chased leaks in many boats and fixed keel screw etc on quite a few boats over the yrs, including doing mine few yrs back.
Will be keel strip screws...
 And most likely the ones where the keel hits the lead roller on the trailer or the one behind it.
May just need a tweak up.. check if when do there is still 'thread' up there.

To find which one.. no rain due for few days/ week,  bung in,  inside flotation bungs and drainage bungs, out boat level, then fill boat with water to smidgen above floor level.
Now leave.. check next day for any damp spot, or may even have a drop water... If there is a breeze this may dry any damp or drop before you see it.
 If there is a leak you will see it.

I had a couple leaking, 1 a drop hanging, which was not always there and a slight damp spot where seeped down further back and was damp. one screw did not pull up.
 On the trailer, on lawn.. more comfortable... moved boat back on trailer as couple screw over rollers. , chocked up off roller about 1" ... Drilled out 10mm maybe be a 12mm ...  ground around the holeback to good glass,
 marked exactly where the center of the dowel will be with felt on the hull.

Now left for week or so for things to dry out

 Mixed up chop stand and resin, then forced pumped hard out up unto the keel... then a tight fitting dowel, pre wetted with resin.. tapped hard up on top of the resin... Let cure, cut dowel low, and glassed over the area, chop strand and gelcoat. sanded reshaped..
Sanded to shape
My brass strip is 2 sections as cant buy strips long enough for full length keel.
 Start at the end of the old strip under the boat, for 1st screw and work back to the bow..
 Drill 1st hole for screw, pack hole with resin, and generous marine sealant on the back of the keel strip.. then next screw to the bow.

Sounds lot work? it isnt.. most is setting boat up, time before doing stuff, and each part doing stuff is 10 to 30 mins tops. over 2 or 3  weeks.

When it comes to bungs,
Good habits are the key.

I've had a few issues over the years with Bunga not in.
Goes against who I am in prep and maintenance and safety, but I'm still a muppet human.
My indiscretions came from in a hurry or overtired and always solo at the ramp.

So I keep and always have wooden bungs.
There tapered all boat shops have them.
I have multiple bilge pumps some on auto.

Remember if you keep the boat moving you will be good.

That real clever - and real simple. Like most great ideas. Never had heard of it.