How do I train 400 IM without losing sprint speed?

My apologies up front for asking a question that has been asked on various different threads over the past couple of years I have been in USMS. I don't remember the responses, however, and can't seem to find the answers in my searches. Here's the deal: I started as a breaststroker and only competed in the three breaststroke events as a newbie. Seven months later, however, I competed in a pentathlon and found I really enjoyed racing the stroke sprints and 100 IM. Last year, I ended up winning my age group and felt even more encouraged to continue working on my other strokes. Recently, I attempted an easy 400 IM in workout to see if I could swim a 100 fly without pausing at the walls. I came in at 7:24 :cane:, but it wasn't the worst in my age group in the rankings! :D Today, after my usual three day post-meet bout of insomnia, I thought, what the heck, I'll try it again. (Yes, I AM crazy!) Again, I took the fly out very easy with the intent of surviving without rescue. My time ended up 7:16, now placing me 56 out of 71 in my age group; still low, but improved. :wiggle: So, now, I'm thinking of giving it some real effort and see where I can go with this... 50 breaststroke is my best event, followed by 100 breaststroke. After that is 50 free and 100 IM. Don't even ask where my 200 breaststroke rates... :bitching: But, my 400 IM, with some effort, will have it beat soon enough. As a six day per week swimmer on pace to beat my goal of 400 miles for the year, how would you recommend I plan my swim week out to train 400 IM without losing breaststroke speed? I average 3,000 yards per workout and currently dedicate Mondays and Fridays to Allen's breaststroke sets or Ande's sprint IM sets that he wrote up for me. Saturday is my recovery day. September thru May, I train in a challenging coached adult program and swim 3,500 - 3,800yards; a mix of speed, endurance, etc. Any advice or suggestions would be most appreciated! (Oh, and, by the way, I am working up to swimming 400m IM and 200yd fly, too.) :afraid:I hope to swim 400IM at Dixie Zone Championships, in August, and see where it goes from there. :worms: