Page 345 - Makino,Tsutusi.DictionaryOfIntermediateJGrammar

ni shitagattelshitagai / ni suginai 271
(= da 1 desu). And V before ni shitagattelshitagai must be Vinf .nonpast.
4. The difference between shitagatte and shitagai is stylistical. The latter is
usually used in written Japanese whereas the former can be used in both
spoken and written style.
[Related Expression]
Vinf .nonpast ni tsureteltsure is an expression very similar to Vinf. nonpast ni
shitagattelshitagai. KS and Exs. can all be rephrased by the former without
changing the essential meaning except KS(B), Exs.(f) and (g), because the
pattern is N ni shitagattelshitagai. The difference seems to be that
Vinf.nonpast ni shitagattelshitagai is more of a written style; whereas
Vinf.nonpast ni tsurete/tsure is more of a spoken style.

S.t. or S.O. is nothing more than nothing more than; not more
what is stated in terms of amount, than; mere; merely; only; just;
degree, status, significance, etc. as little / few as; that's all
[REL. dake da; tada no]
+ ~ Sentences
~
e

(This is nothing more than my personal opinion.)