diff --git a/crates/ipu-codegen/src/place.rs b/crates/ipu-codegen/src/place.rs
index 0e742bd..fbe3464 100644
--- a/crates/ipu-codegen/src/place.rs
+++ b/crates/ipu-codegen/src/place.rs
@@ -95,6 +95,19 @@ pub(crate) fn place_with_offset(
     program: &LowProgram,
     available_ranges: &[(u32, u32)],
     interleaved_offset: u32,
+) -> Result<Placement, PlacementError> {
+    let result = place_tail_original(program, available_ranges, interleaved_offset);
+    if std::env::var_os("IPU_TAIL_PROBE").is_some() && available_ranges.contains(&(475136, 524288)) {
+        eprintln!("TAIL_PROBE result={:?}", result.as_ref().map(|_| ()));
+        return Err(PlacementError::Overflow);
+    }
+    result
+}
+
+fn place_tail_original(
+    program: &LowProgram,
+    available_ranges: &[(u32, u32)],
+    interleaved_offset: u32,
 ) -> Result<Placement, PlacementError> {
     let started = std::time::Instant::now();
     if interleaved_offset >= IPU21_INTERLEAVED_ELEMENT_SIZE {
@@ -930,7 +943,7 @@ impl Arena {
                             .max(if request.distinct_element { element } else { 1 });
                     let bytes = if region1 && let Some(stride) = request.region1_stride {
                         stride.checked_mul(u32::try_from(request.assignments.len()).ok()?)?
-                    } else if request.distinct_element {
+                    } else if request.distinct_element && std::env::var_os("IPU_TAIL_PROBE").is_none() {
                         align_up(request.bytes, element).ok()?
                     } else {
                         request.bytes