I agree with using the TDM pack if you're playing solo, that's about the only mod I use for SP. And of course, up the difficulty and bonus. One other thing I do that's not mentioned here is to not use all your racial points during setup or somehow otherwise 'handicap' your race. If you're playing a 5000 point game, only use 2500 or something like that. Or better yet, don't use any and use all the default racial settings - don't adjust your points any and see if that changes anything; I bet it does
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With a little tweaking and imagination, you *can* make solo play challenging and yet not have a 'cheating' AI.