The same was true (so I was told when I did the conversion) of the Bell 206B - same engine as our BO 105s (RR Allinson). Have we 'blown' the IGVs here because we have not allowed the residual temp to reach 150? I often wait for 200 and then start but wait until 17% N1 and an indicated temp of below 100 - it starts up well within limits.
I think you may have answered your own question.
In my own experience with the Allisons it was standard practice to 'motor' the starter unit (with the igniters off) until the residual TOT was down to around 50°c and thereafter to initiate a normal start.
By employing this separate 'motoring' of the starter you will find that it is unnecessary to allow the N1 to travel beyond normal and .. it has the added benefit of further reducing the residual TOT.