I would prefer 8 or 10 nt UDIs instead. Is this possible?

Lexogen UDI 12 nt Sets contain a unique nested feature enabling adjustable index read-out lengths (the longer the index read-out, the better the error correction). The UDIs are 12 nucleotides long, however, the superior error correction feature can also be used if only 8 or 10 nucleotides of the index are read out, if the i5 index was read out in the correct orientation see Figure 1 and also https://faqs.lexogen.com/faq/how-do-i-choose-the-right-lexogen-udi-12-nt-unique .

Figure 1 | Optional read-out lengths for Lexogen UDI 12 nt Sets.