diff --git a/README.md b/README.md
index 13f0fe9..937f511 100644
--- a/README.md
+++ b/README.md
@@ -11,9 +11,13 @@ Everything lives on a ZFS dataset mounted at `/minecraft`.
 ```bash
 ./deploy.sh -n "Opengames" -a themiro \
     -u https://games.abdelbaki.eu/mods \
-    -N 21.1.72 --accept-eula
+    --accept-eula
 ```
 
+The NeoForge version is resolved automatically — the newest stable build in the
+series matching your Minecraft version, from the NeoForged maven. Pin one with
+`-N 21.1.248` if you'd rather not track latest.
+
 Then:
 
 ```bash
@@ -35,6 +39,23 @@ server address already filled in.
 | `mc-refresh-restart.sh` | you | Re-sync the pack after changing mods, then restart |
 | `build.sh` | you | Builds the release zip |
 
+## Memory
+
+The heap defaults to 13 GB (`-X`/`-x` to change it). `-XX:+AlwaysPreTouch` means
+the JVM commits the whole heap at startup rather than growing into it.
+
+On a ZFS host, cap the ARC before running a heap this large — ZFS defaults to
+using up to half of RAM for cache, which will fight the JVM for the same pages:
+
+```bash
+echo "options zfs zfs_arc_max=2147483648" | sudo tee /etc/modprobe.d/zfs.conf
+sudo dracut --force && sudo reboot
+```
+
+That pins the ARC to 2 GB. On a 16 GB box, 13 GB heap + 2 GB ARC leaves ~1 GB
+for everything else, which is tight — drop the heap to 10–11 GB if the host
+does anything besides run the server.
+
 ## Requirements
 
 - Fedora (or any systemd distro; `dnf` calls need swapping otherwise)
diff --git a/deploy.sh b/deploy.sh
index f338569..9a38d8f 100755
--- a/deploy.sh
+++ b/deploy.sh
@@ -13,8 +13,8 @@
 
 set -euo pipefail
 
-NAME=""; AUTHOR=""; BASEURL=""; NFVER=""; MCVER="1.21.1"
-SHARE="/minecraft"; XMX="8G"; XMS="4G"; ACCEPT_EULA=""
+NAME=""; AUTHOR=""; BASEURL=""; NFVER="latest"; MCVER="1.21.1"
+SHARE="/minecraft"; XMX="13G"; XMS="13G"; ACCEPT_EULA=""
 HERE="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
 
 die()  { echo "error: $*" >&2; exit 1; }
@@ -51,7 +51,7 @@ sudo -v || die "sudo is required"
 
 step "1/2  Minecraft systemd service"
 sudo "$HERE/mc-service-setup.sh" \
-    -s "$SHARE" -A "$USER" -X "$XMX" -x "$XMS" \
+    -s "$SHARE" -A "$USER" -X "$XMX" -x "$XMS" -m "$MCVER" \
     ${NFVER:+-N "$NFVER"} ${ACCEPT_EULA}
 
 step "2/2  packwiz pack and player guides"
diff --git a/mc-service-setup.sh b/mc-service-setup.sh
index b0cfd39..125c5cd 100755
--- a/mc-service-setup.sh
+++ b/mc-service-setup.sh
@@ -18,9 +18,10 @@ set -euo pipefail
 
 SHARE="/minecraft"
 MCUSER="minecraft"
-XMS="4G"
-XMX="8G"
-NFVER=""                  # set to install the NeoForge server
+XMS="13G"
+XMX="13G"
+NFVER=""                  # version, or "latest" to resolve one; empty = don't install
+MCVER="1.21.1"            # only used to pick the matching NeoForge series
 ADMIN=""                  # human user who authors the pack on the share
 ACCEPT_EULA=0
 UNIT_DIR="/etc/systemd/system"
@@ -38,6 +39,7 @@ while [ $# -gt 0 ]; do
         -x|--xms)       XMS="${2:-}"; shift 2 ;;
         -X|--xmx)       XMX="${2:-}"; shift 2 ;;
         -N|--neoforge)  NFVER="${2:-}"; shift 2 ;;
+        -m|--mc)        MCVER="${2:-}"; shift 2 ;;
         -A|--admin)     ADMIN="${2:-}"; shift 2 ;;
         --accept-eula)  ACCEPT_EULA=1; shift ;;
         -h|--help)      usage 0 ;;
@@ -88,6 +90,37 @@ fi
 
 # -------------------------------------------------------------- neoforge ----
 
+# NeoForge versions are <mc-minor>.<mc-patch>.<build>, so 1.21.1 -> 21.1.x and
+# 1.21 -> 21.0.x. Resolve the newest stable build in that series from the
+# NeoForged maven; the [0-9]+$ anchor keeps betas out.
+resolve_neoforge() {
+    local mc="$1" prefix rest meta
+    rest="${mc#1.}"
+    case "$rest" in
+        *.*) prefix="$rest" ;;
+        *)   prefix="${rest}.0" ;;
+    esac
+
+    meta="$(curl -fsSL --max-time 25 \
+        https://maven.neoforged.net/releases/net/neoforged/neoforge/maven-metadata.xml 2>/dev/null)" \
+        || return 1
+
+    printf '%s' "$meta" \
+        | grep -oE '<version>[^<]+</version>' \
+        | sed -e 's/<[^>]*>//g' \
+        | grep -E "^${prefix//./\\.}\.[0-9]+$" \
+        | sort -V | tail -1
+}
+
+if [ "$NFVER" = "latest" ]; then
+    info "resolving latest NeoForge for Minecraft $MCVER"
+    NFVER="$(resolve_neoforge "$MCVER" || true)"
+    [ -n "$NFVER" ] || die "could not resolve a NeoForge version for Minecraft $MCVER
+     Pick one manually from https://projects.neoforged.net/neoforged/neoforge
+     and pass it with -N <version>."
+    info "resolved NeoForge $NFVER"
+fi
+
 if [ -n "$NFVER" ]; then
     info "installing NeoForge $NFVER server into $SHARE"
     url="https://maven.neoforged.net/releases/net/neoforged/neoforge/${NFVER}/neoforge-${NFVER}-installer.jar"