I would be alright. I run 25 tyres on DP18, originally intended for 18-23 tyres. No problem at all!
Rigida site specifies 18-25 for DP18s
They're 13mm interior width
Table at Sheldon Brown also says 18-25 for 13mm interior rims.
http://www.sheldonbrown.com/tyre-sizing.html#width
Also states "Many cyclists exceed the recommended widths with no problem"
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Rigida site specifies 18-25 for DP18s
They're 13mm interior width
Table at Sheldon Brown also says 18-25 for 13mm interior rims.
http://www.sheldonbrown.com/tyre-sizing.html#width
Also states "Many cyclists exceed the recommended widths with no problem"