diff --git a/test_runner/performance/test_perf_many_relations.py b/test_runner/performance/test_perf_many_relations.py
index 9204a6a740..87316b28e5 100644
--- a/test_runner/performance/test_perf_many_relations.py
+++ b/test_runner/performance/test_perf_many_relations.py
@@ -80,7 +80,12 @@ def test_perf_simple_many_relations_reldir(
     """
     Test creating many relations in a single database.
     """
-    env = neon_env_builder.init_start(initial_tenant_conf={"rel_size_v2_enabled": reldir != "v1"})
+    env = neon_env_builder.init_start(
+        initial_tenant_conf={
+            "rel_size_v2_enabled": reldir != "v1",
+            "rel_size_v1_access_disabled": reldir == "v2",
+        }
+    )
     ep = env.endpoints.create_start(
         "main",
         config_lines=[
@@ -108,10 +113,6 @@ def test_perf_simple_many_relations_reldir(
             == "migrating"
         )
     elif reldir == "v2":
-        # only read/write to the v2 keyspace
-        env.pageserver.http_client().timeline_patch_index_part(
-            env.initial_tenant, env.initial_timeline, {"rel_size_migration": "migrated"}
-        )
         assert (
             env.pageserver.http_client().timeline_detail(env.initial_tenant, env.initial_timeline)[
                 "rel_size_migration"
diff --git a/test_runner/regress/test_compatibility.py b/test_runner/regress/test_compatibility.py
index 635a040800..539bbcaab8 100644
--- a/test_runner/regress/test_compatibility.py
+++ b/test_runner/regress/test_compatibility.py
@@ -581,12 +581,10 @@ def test_historic_storage_formats(
         # This dataset was created at a time where we decided to migrate to v2 reldir by simply disabling writes to v1
         # and starting writing to v2. This was too risky and we have reworked the migration plan. Therefore, we should
         # opt in full relv2 mode for this dataset.
-        for timeline in timelines:
-            env.pageserver.http_client().timeline_patch_index_part(
-                dataset.tenant_id,
-                timeline["timeline_id"],
-                {"force_index_update": True, "rel_size_migration": "migrated"},
-            )
+        env.pageserver.http_client().patch_tenant_config(
+            dataset.tenant_id,
+            {"rel_size_v1_access_disabled": True, "rel_size_v2_enabled": True},
+        )
 
     # Import tenant does not create the timeline on safekeepers,
     # because it is a debug handler and the timeline may have already been
diff --git a/test_runner/regress/test_pg_regress.py b/test_runner/regress/test_pg_regress.py
index 374514b9bd..c2a7c02f2f 100644
--- a/test_runner/regress/test_pg_regress.py
+++ b/test_runner/regress/test_pg_regress.py
@@ -124,6 +124,7 @@ def patch_tenant_conf(tenant_conf: dict[str, Any], reldir_type: str) -> dict[str
     tenant_conf = tenant_conf.copy()
     if reldir_type == "v2":
         tenant_conf["rel_size_v2_enabled"] = True
+        tenant_conf["rel_size_v1_access_disabled"] = True
     else:
         tenant_conf["rel_size_v2_enabled"] = False
     return tenant_conf
@@ -440,14 +441,6 @@ def test_tx_abort_with_many_relations(
         ],
     )
 
-    if reldir_type == "v2":
-        # v2-only mode instead of v1-v2 validation mode
-        env.pageserver.http_client().timeline_patch_index_part(
-            env.initial_tenant,
-            env.initial_timeline,
-            {"rel_size_migration": "migrated"},
-        )
-
     # How many relations: this number is tuned to be long enough to take tens of seconds
     # if the rollback code path is buggy, tripping the test's timeout.
     n = 5000