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I use the PX POD ones and they are pretty decent.
Have a Tempest V3 in large. The original (light grey) large (5.3l?) Apidura frame bag (with three top straps, not the later one) fits perfectly and is never removed. It's very light, robust and held on with 7 straps so stays put on offroad descents. It leaves just enough space for a 500ml bottle in the downtube cage. Can rub the knees a bit when overstuffed but it's about as comfortable as a large strapon could ever be.
If I were buying now, I'd probably look at Lomo for stonking VFM.
I had an alpkit setup on mine
Slightly got in the way of the water bottles but otherwise fab, good size, secure, easy access.
Alex - you could move the rear bottle down using a Wolftooth B-Rad.
I've a Freeranger and while the Podsacs fits it's too short for my XL, so I recently got this:
https://alpkit.com/products/deluge-frame-bag
If you take a look down the link you'll see an On One XL Ti bike - so I kinda guessed it'd fit mine, and does.