Chinese Han Dynasty Crossbow 300lbs 20" powerstroke

I am hoping to make a 300lb  "Han dynasty style" Crossbow with a powerstroke of around 20 inches (so around 25 inch draw length). Considering the prices of Horn and sinew, I am most likely making the bow prod out of fibreglass or PVC, unless I can purchase a composite bow of that draw weight/length. Due to the material choice, the goal of this is to test the theoretical power of a Han crossbow by making similar dimensions in Powerstroke and draw weight.
So far on the internet, I have not found a single example of such a crossbow replica, so hence this project. (Most examples of these replicas look like they have a maximum draw weight of under 70lbs )
Due to my lack of experience in fibreglass bowmaking, hoping to get some expertise knowledge from anyone. Would be great to know where I can get fibreglass(and the specific type) realistically for this type of monstrous prod. Just hoping to know when I walk into a FRP fibreglass supplier shop for construction, I can tell them the exact fibreglass type to order. Most likely for my first attempt the prod will not be re-curved and will have a simple D shape for simplicity. I would be glad to add siyahs but without any experience please contact me for suggestions on how to attach the siyahs for such a heavy draw weight as I am worried about the glue. Considering the modulus of elasticity of fibreglass, the bow prod would need to be around 5 feet long with a average width of 3 inches I'd assume.
My Main concern is making the crossbow trigger right(will be using steel for trigger parts due to acessibility) and I will be using dacron for the string material. So clearly you can see the focus is less on historical accuracy, but rather to test the theoretical power of such a weapon.

If I had the historically accurate materials and skills to make a horn and sinew replica, I would be glad to. But so far I have to start somewhere. I have made crossbows out of spring steel before but nothing asiatic.

The article that inspired me to make this:  cannot post link due to new member

Also if you are wondering how is this different from a modern fibreglass bow? Most of them have a draw weight limit of 200lbs but their bow prod is only 3 feet long. Considering the elasticity of fibreglass, it cannot have a long powerstroke while being that short. By increasing the bow prod to 5 ft or 6 ft, we can increase the maximum elastic deflection, hence more powerstroke, while sacrificing portability.

btw also making a repeating crossbow version with a 110 lb  horsebow with a 26 inch draw length. It will probably end up being more of an artillery piece but it will be a lot of fun.

The crossbow shown in my avatar picture is well over 200 lb draw at 18", with a solid fiberglass prod 28" long.  I used what is known in the US as a "fiberglass chainlink fence tension bar" approximately 3/4" wide by 1/2" thick.  I combined 3 strips of fiberglass in the style of an ancient Chinese "loose laminate" prod (originally strips of bamboo).  The loose laminate structure lets you make a significantly stronger prod with a shorter length.

You can read about my design and build here:

https://thearbalistguild.forumotion.com/t945-loose-laminate-pinlock-build?highlight=pinlock

speaking of Chinese repeating crossbows: I once saw photos taken at the Taku Forts, right after the Peking Siege of 1900.  There were a number of repeating crossbows lying about in the wreckage.  That doesn't preclude their being placed for photographic effect, but at least it's evidence such weapons were available for the forts' defenders.  It's always been my contention they would be most useful for point-defense, like gateways, passages, doors, etc.  Payne-Gallwey said they often used poisoned darts.  A marvelous weapon, lots of fun to play with in the back yard... without the poisoned darts.  Geezer.