Horizontal sliding dropouts how do I mount rear mech

As per title I’ve got a Cotic Roadrat with an 8 speed Alfine rear hub which I’m thinking of converting to 1 x 11.
The frame has horizontal sliding dropouts so was wondering what I need to do to allow me to fit a 11 speed rear mech and ideally bolt through axle without having the frame modified?

https://www.bikemonger.co.uk/problem-solvers-chain-tensioner-with-hanger-13300-p.asp

Just push the axle all the way to the front of the sliding dropout and clamp it in place. Fit your derailleur hanger and away you go. This was with a regular qr wheel mind. You might need to adjust the brake caliper position too.

I emailed Cotic to ask as I was in the same position as you.

Similar vein to the above but possibly in stock is the sun xcd one. No idea if it works but spotted it a while ago and have no need for it.
https://www.velovitality.co.uk/collections/transmission/products/sunxcd-horizontal-dropout-mech-hanger

I’m using something very much like that on an old road rat. A bit annoying when the rear mech escapes as you take the back wheel off but you get used to it.

If you can convert your hub to take it a 10mm ‘through axle’ makes it easier to get the wheel out if you use mudguards- take the axle out and the wheel can drop down.

Cheers guys afew options for me there to explore.

Cotic did used to sell a tensioner & hanger combo for the Roadrat.
No idea if they have any in stock anymore, but might be worth emailing them.
This one: