Will a rectangular sleeping pad fit, or am I better off with a mummy shaped pad?

Tech Specs:

Material:

[Upper] No-see-um mesh; [Floor] Hydroseal-200 coated taffeta 

Freestanding:

Yes 

Poles:

One shock-corded 

Pole Material:

Delrin 

Doors:

One full-zip opening 

Clip/ Sleeve:

Sleeve 

Floor Space:

[L x W] 89in x 25in, 225cm x 64cm; [Area] 15.45sq ft, 1.44sq m 

Interior Height:

18in, 46cm; *74in, 190cm maximum shoulder circumference 

Vestibule Space:

N/A 

Seam Sealed:

Yes 

Bathtub Floor:

No 

Ventilation:

No-see-um mesh 

Packed Size:

14in x 3in x 4in (36cm x 8cm x 10cm) 

Weight:

16oz, 454g 

Recommended Use:

Ultra-lightweight summer backpacking, camping, adventuring, star gazing 

Warranty:

Infinite 

Country of Origin:

China