Update a bit the USB installation design doc.

wiki/src/contribute/design/installation.mdwn

@@ -40,7 +40,7 @@ Two alternatives booting methods have been investigated:
 
 We have settled on the *copy ISO's content* way, mostly because it is overall
 simpler, more robust, and allows
-implementing [[!tails_todo incremental_upgrades]] relatively easily.
+implementing [[contribute/design/incremental_upgrades]] relatively easily.
 
 Partitioning
 ============
@@ -56,11 +56,13 @@ The storage device is partitioned using [GPT](https://en.wikipedia.org/wiki/GUID
  * Partitions can be labeled. The [[design/persistence]] setup tools can
    easily detect the right partitions without blind tries.
 
-The system partition (holding Tails) has a size of 1.5 GB, with the
+The system partition (holding Tails) has a size of 2.5 GB, with the
 following estimates:
 
  * Tails ISO: 1GB
- * 3 [[!tails_todo incremental_upgrades desc="incremental upgrade kits"]], 60 MB each: 180MB
+ * 3 [[incremental upgrade kits|contribute/design/incremental upgrade]], 200 MB each: 600MB
+ * free space needed to install an incremental upgrade kit: 2 * 200 MB
+   = 600 MB
 
 The Tails system partition uses a FAT32 filesystem, mainly because it is the
 one supported by SYSLINUX we may easily create, in a programmatic manner, from
@@ -124,11 +126,11 @@ We have `.desktop` files for the following usecases:
 Why a fork of liveusb-creator?
 ==============================
 
-After an initial [[!tails_todo usb_install_and_upgrade/archive desc="roundup of existing tools"]],
+After an initial [[roundup of existing tools|blueprint/usb_install_and_upgrade/archive]],
 we decided to use Fedora's `liveusb-creator` as a basis, for reasons that are now
 obsolete due to more recent design choices. While we did most of our initial
 adaptation work on liveusb-creator with future upstreaming of our changes in
 mind, it proved to be hard, and future extension seems now out of question.
-Our [[!tails_todo usb_install_and_upgrade desc="future plans"]] include moving to another
+Our [[future plans|blueprint/usb_install_and_upgrade]] include moving to another
 piece of software as a basis, and hopefully working more closely with this
 future upstream of ours.