Bullpup design question

[customcutter]

I am making a Bullpup stock for my BT 65.  The only after market stock I've seen on Youtube has grub screws that tighten from the bottom of the upright to the air cylinder.  It also has a bolt that tightens through the bottom of the stock, and probably another that holds the scope rail on top. 

Some Bullpup pictures I've seen show a slot machined from the bottom hole for the air cylinder to the upper hole for the barrel.  To me the only reason for doing it would be to clamp the upright to either the air cylinder, the barrel, or both.

So, my question is does your Bullpup have one upright or two?  And does it clamp to the air cylinder, barrel, or both?

Thanks in advance,
Ken

[Motorhead]

Due to flex between barrel and air cylinder and needing to have solid scope alignment the most successful designs have 2 scope riser portions clamping tube to barrel with scope resting on top of the very rigid assembly.

2nd best would be a single riser clamping tube/ barrel with a scope rail solidly connected to the receiver area.

JMO ...

[Zebra]

Most PCP bullpups connect to the stock through a pair of metal barrel bands. The bands are clamped to the air cylinder but the barrel threads through them too. This serves the function of making sure the scope rail is properly aligned with and parallel to the barrel.

The barrel bands also attach to the trigger linkage mechanism. This makes the most sense if your bullpup stock is wood. On most of the firearm bullpup stocks I have seen, the trigger linkage mechanism is in the actual stock and not connected to the action, but firearm bullpup stocks are rarely made of wood.

My advice, if you aren't a skilled metal-worker, would be to bed and connect your BT65 to the stock using the same screw holes as it uses for it's current stock.

I would then attach the trigger linkage mechanism to the stock itself. I did this for an AT44 and it worked well. The absolute easiest way I found to do it was using a Mako speargun AR handle frame + their trigger rod. The handle frame is aluminum with a trigger guard and AR grip adapter. The top plate has a groove already machined in for the trigger rod. All you have to do is drill some holes to attach it.