I have done something similar with 10'fiberglass rods. You can get them pretty deep with these. I used small hose clamps to attach them to the tall H stands.

There ya go lot easier then screwing around cutting poles and building a Teepee. LOL

The metal superstands have their place but if you read what I wrote before about trapping culverts they will not work where the tee pee set works.I don't know any serious beaver trappers that don't have a supply of tamarack poles in the sleigh for many uses.

I have zero Tamarack poles when beaver trapping.

I often have a good supply of small beaver chewed sticks along when trapping open water.

Some of us trap when there is ice. Your half submerged set doesn't work too well 85% of our season!!!

I will do the same in open water.

I always have poles,as do all beaver trappers here.Need them for countless applications.Pull up to the gas station with the truck,and see another with a few poles sticking out the back you know hes a beaver trapper.
You can see a few applied as block sticks in the multiple beaver set along with the superstands.

Aix,the reason we use tamarack is when they are dry they are light as a feather and hard as steel.They are also basically the same diameter for 10 feet or more and straight with no branches when cut in a thicket.1 inch diameter dry pole has tons of uses on a winter trapline.
I'm sure you have another species where you are,but like was said on here earlier unless you are trapping under ice there are other sets on the surface that will take beaver,so not really necessary to trap deep water runs.

Boco why won't those metal H stands work when trapping the mouth of a culvert?
I build my own H stands and they are built to fit different situations on my line.

Some of our culverts are 1 to 3 feet off bottom and under 3 feet of water.You would never know there was a culvert there if not for the two spots of open water at each side of the bush rd.
Should have some ice in a couple weeks,maybe I'll set up a couple and take a few pics.Its hard to explain but easy to show.

I understand your situation. WE have the same thing here. I just build my H stands with longer legs. The depth of the water under the lower lip of the culvert Is always the same. So building the stand to fit the situation Is pretty straight forward.

Do you guys wire your trap off to somewhere on shore or do those stands and poles hold enough to not fall over?

Just wire a 2 liter bottle to the trap extentions with a long enough cable or light wire.

When can't be secured on land or bush, and your in a boat.

I have a long cable attached to mine so I can stake it on the house, shore, or on ice if necessary. Kirk has a great idea if you can't.

In winter they freeze in,but we use a safety pole in case one gets caught before it freezes so he cant pull everything under the ice.
In open water,at the house,i use a 3rd pole shoved into the house and wired off at the cross.
At a culvert,just a wire to brush or stake.

WE secure a C clamp (beam clamp) to the lip of the culvert. Then we can put a stiffener out to the stand and also secure the trap to the clamp.

The first thing I did with my tall H frames was to add on about 6" to the legs.

I usually upgrade my stack of tamarack poles every year. I use them for beaver or snare poles. These are driven into trails before freeze up. Then I don't need to carry so much when the time comes to hang cables.