Definitely move from SHA1 to SHA256 for both phases, and you should probably increase your Diffie Hellman Group to 19+ for the supposedly more secure Elliptic Curve key calculations instead of the older MODP. May also want to use AES-GCM-128 for Phase 2 which is slightly more efficient, unless we are talking military applications where people will literally die if someone can crack the encrypted traffic in a reasonable timeframe, then use AES-256 for Phase 2 with PFS. These changes shouldn't cause a noticeable performance impact and I believe are a reasonable balance between performance and security in most cases.
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