ssl-opt.sh: increase proxy mtu sizes to contain entire datagrams

diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 9c904c3..f70a85c 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -5819,7 +5819,7 @@
 requires_config_enabled MBEDTLS_ECDSA_C
 requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
 run_test    "DTLS fragmenting: client-initiated, server only (max_frag_len), proxy MTU" \
-            -p "$P_PXY mtu=1024" \
+            -p "$P_PXY mtu=1110" \
             "$P_SRV dtls=1 debug_level=2 auth_mode=none \
              crt_file=data_files/server7_int-ca.crt \
              key_file=data_files/server7.key \
@@ -5867,7 +5867,7 @@
 requires_config_enabled MBEDTLS_ECDSA_C
 requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
 run_test    "DTLS fragmenting: client-initiated, both (max_frag_len), proxy MTU" \
-            -p "$P_PXY mtu=1024" \
+            -p "$P_PXY mtu=1110" \
             "$P_SRV dtls=1 debug_level=2 auth_mode=required \
              crt_file=data_files/server7_int-ca.crt \
              key_file=data_files/server7.key \