BACKGROUND: Transcatheter aortic valve (TAV) leaflet modification can reduce the risk for coronary obstruction caused by the leaflet neoskirt created during TAV-in-TAV procedures. OBJECTIVES: The aim of this study was to evaluate the leaflet splay geometry created by different leaflet modification techniques across the spectrum of TAV-in-TAV combinations. METHODS: BASILICA (bioprosthetic or native aortic scallop laceration to prevent iatrogenic coronary artery obstruction during TAV replacement), balloon-assisted BASILICA (BA-BASILICA), and UNICORN (undermining iatrogenic coronary obstruction with radiofrequency needle) were simulated on the bench in short-in-tall, short-in-short, and tall-in-short TAV-in-TAV combinations. High-resolution images were used to evaluate leaflet splay geometry and measure the leaflet splay area. Splay obstruction caused by the skirt from the index or second TAV was subtracted from the leaflet splay area to define the functional splay area (FSA). Factors influencing the FSA were evaluated. RESULTS: Across all tested TAV-in-TAV combinations, BASILICA and BA-BASILICA created similar vertical V-shaped LSAs, measuring between 19.2 and 64.9 mm2. UNICORN created the largest LSAs for short-in-tall and short-in-short combinations, measuring 2 to 10 times larger than those created with BASILICA and BA-BASILICA. UNICORN with intraleaflet deployment was not feasible for tall-in-short combinations and required predeployment balloon laceration of the leaflet, which created an unpredictable splay outcome. The greatest degree of splay obstruction, up to 93%, was observed for tall-in-short combinations, resulting in the smallest FSA after BASILICA and BA-BASILICA. The FSA following leaflet modification could be improved by ensuring commissural alignment and lowering the implantation depth of the second TAV. CONCLUSIONS: BASILICA and BA-BASILICA create similar sized vertical splays in the leaflet neoskirt, whereas UNICORN generates larger FSAs but only when intraleaflet deployment is feasible. The design, alignment, and implantation depth of the second TAV may influence the FSA after leaflet modification.