Hi
@
backpack
,
This kind of information is totally within the existing pictures posted within the forums. See
my post (#25, dated 04-07-2015) from the
question about spiff kit deluxe thread.
I've included an 8.75 x 6 x 1.25 in library book in the top half of the open DSK in this picture, where the shelf with attached Lush samplers is simply folded up, and lays fairly flat.
You can read the entire thread and its links, if you want details about how it was configured, because the excerpted comment for that image was in the context of packing up the accessory, configuring items on the folding shelf (LUSH samplers), and closing the Spiff Kit Deluxe with the book in the top half, and all the items carried below.
There are also lots of threads with pictures that compare the two sizes of Spiff Kits, and that also answer questions like whether Moleskine notebooks fit. (I know that’s not
@
m_cycle
’s question). Both Spiff Kits are larger than the HLT2. See the
Having trouble deciding on spiff kit
thread, since I think the first comparison post picture of the two sizes that I gave in the response is no longer viewable as an image in its source thread, where it was posted via TapaTalk upload. (Since I saved it as a forum attachment when I referenced it as a sample of the pictures I thought might be useful, it’s still visible in my post. This is the image of the Iberian Spiff Kit Deluxe and the Ultraviolet Spiff Kit Standard that I think may have originally been posted by
@
Walker
).
Also,
@
backpack
posted a similar request about having an accessory that could be used as a notebook cover in the
2018 wishlist thread (#233, dated 02-11-2018), and there are pictures and discussions around that post. My reply, in
post #236, went back to link earlier photos showing a standard Moleskine in the Spiff Kit Standard:

but also discussed other sizes of accessories that are also larger than the HLTs (First and Second Aid Pouch).
For
@
m_cycle
, I’d have to check the Lihit Lab Twist Notebook dimensions, but my preferred recommendation for something to store A5 journals was the (retired) Stowaway Aether Packing Cube. See my answer in the
A5 in a TSS? thread of 2018
If you want to see more pictures of how the retired Aether packing cubes work with other A5 notebooks, as well as how I can use these in the back pockets in either the L12 or L15 sizes Luminaries to vertically stack items, take a look at the images in
my post (#1733, dated 02-22-2019) in the (long!)
Discussion of New Colors, New Designs thread.
For specific reference to the HLT2, the largest notebook that I comfortably use that fits under the inside mesh pocket is the Leuchtturm1917 Planner (or similar thinner form factor notebooks). I had to
match a pack up request for the Icon by @GoNavy, so I can tell you its exact dimensions
You can see what I mean by a “comfortable” fit by looking in the
HLT 2 sizing thread pictures for the same Notebook.
Slightly larger books can fit inside the open HLT2, but they are tight.
HTH
moriond
ETA: There are more helpful pictures in the last set of links. It’s just that the number of copy and pastes it takes to assemble all these answers on an iOS device can get excessive. They’re not hard for me to recall or find, but getting out the embedded images just takes a lot of extra work. BTW, if I quote without separately pasting in exact links to forum URL attachments, there is significant performance degradation when quotes are being viewed outside of their parent threads. But it’s just a lot more work to give exact URLs for absolutely every image that someone wants to see, although I know that a lot of people tend to ignore the parts of a post where the actual images are not provided in detail again