I happened to be reading through Alpkit's magazine thing that they send out and there was mention of a dropper post compatible seat bag. A check on their site and ... https://www.alpkit.com/products/koala-7 From the pictures (look at those under "more images") it looks like there's an extra set of rails, the Exo-rail, in the seat clamp beneath the saddle rails and this forms a loop that a sleeve in the bag slides onto with a Wolf Tooth Valais like collar on the post itself.

Clearance might be a problem with full suspension bikes - I just checked mine, 280mm. The bike has 80mm of travel so that's now an effective 200mm, the product page states 180mm minimum clearance so I'd only be able to use 20mm of travel on the dropper. Hmm. I think if it was 50mm then it would be a goer. Not so much a problem on the hardtail for me at least - there'll be very similar clearance so I'd be able to use the full travel of the dropper (less the width of the collar).

There's no product page for the Exo-rail itself yet though.

Being a hobit, saddle packs have always been difficult to fit, especially with 29" wheels. On my hardtail I can get away with a small wildcat seat pack + 8L drybag, with just minimal clearance, without a dropper. On the Spearfish I could get away with an Alpkit Kowari (3L), but now I have fitted a dropper, at max drop (with a Woolthtooth valais thing fitted), I have 90mm clearance between saddle rails and tyre, with the rear wheel at max travel. The only thing I can fit (and yet to test) is a small Defiant Toklat (1.2L), from Backcountry.Scot, which is about the right size for tools & spares. So it is back to a small backpack if I want to use FS and a dropper, which is not such a bad thing as it often better to have weight off the bike on the sort of techy descents this set-up is optimised for anyway.

What would be ideal is a seat pack design that has two support rails attached to the top of the seat-post/saddle rails, extending back at saddle height, with the bag mounted above these rails... difficult to explain without a sketch, and maybe tricky to manufacture whilst maintaining strength and minimal weight. The closest thing I can find is this, except it is not integrated with the bag, heavy, and looks sub standard!
https://www.arkel-od.com/en/arkel-randonneur-rack.html

Have you got an old seat post and seat clamp you can sacrifice. Quite liked how simple this idea was.
https://goo.gl/images/oBpJYx

WTF!

Aside from making my eyes hurt looking at it, even if it lasted more than 5 minutes, it would not resolve the problem with clearance.

I've got 17.5 cm saddle rail to tyre clearance on the fat bike.

I've just fitted on of these...

http://www.bedrockbags.com/gear/black-d ... r-seat-bag

The non dropper version - same bag and bracket just without the seat post collar.

Lovely quality....

There's also a new mini-harness and bag from Revelate. Probably still too big for the hobbits though.

The problem with a bag at above-saddle height would be swining a leg over it - and potentially trying to get off the back a little on the sort of descents a FS might encourage.

I've been using pipe insulation so that I can use a dropper and my seat pack. Doesn't often get an outing, usually use a normal seat post, but it gives me an inch or two when required

Porcelain Rocket Albert here - works very well. Almost full drop for me on my Reverb, but it is one of the short drop versions.

I’ve recently got one of the new rogue panda ripsey bags. Only requires 130 mm of clearance.
Only available direct so some expensive shipping and import fees must be paid to get it sent over here!

Anyway, here's the Exo-rail in all its glory - https://www.alpkit.com/products/exo-rai ... ing-system

The clearance for the bags is different to that I originally quoted from the Koala 7 product page: it's 150mm for the 7 litre and 180mm for the 13 litre.

Craig - my wife has that Arkel Randonneur seat rack but uses it set a bit higher, probably at about 100mm below the top of the saddle. It's very solid with no sway. I just checked the clearance on her Stooge: 170mm, so the small Koala might suit her.

whitestone wrote:Anyway, here's the Exo-rail in all its glory - https://www.alpkit.com/products/exo-rai ... ing-system.

Scott Felter would be flattered I’ve a porcelain rocket Mr Fusion ( no dropper) if a needed a dropper compatible bag I’d get the Albert. PR may no longer be in the custom game but they are still coming out with real innovative products, still made in house by a small team. All credit to alpkit for making affordable kit but I think I’d rather support the guys who put all the hard work in.

I've been wondering about one of these ... http://www.bikepacking.com/gear/rockgei ... la-review/

I like the idea of no additional hardware - anyone on here used one?