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NEW YORK (CNN/Money) - I'm currently investing in a lifecycle mutual fund. I like the convenience of not having to worry about asset allocation. Is there an easy way to add some diversification without altering the overall asset allocation? Am I correct in wanting to diversify further?

-- Ryan, Springfield, Virginia

First, let me quickly explain what a lifecycle fund is so people not familiar with them don't think I'm talking in some strange foreign language.

Basically, lifecycle funds divvy up their holdings among a variety of different asset classes -- large-company stocks, small-company stocks, foreign shares and bonds. Fund companies that offer lifecycle funds typically offer a menu of them, typically an aggressive fund (say, 70 percent or more in stocks), a moderate one (50 to 70 percent stocks) and a conservative fund (30 to 50 percent in stocks).

There's another type of fund that works on the same principle, but has an extra twist. I'm talking about target retirement funds. With these funds, you choose a fund with a date that roughly corresponds to the year you plan to retire -- 2020, 2030 or whatever -- and you get a fund that invests in a mix of stocks and bonds appropriate for someone your age.

But here's the twist. With a target fund, that stock-bonds mix automatically becomes more conservative as you age, the idea being that when you get closer to retirement, you don't want to invest quite as aggressively as you do during your career. For more on how these funds work, click here.

Alas, since there's no official arbiter of fund category names, people often use these terms interchangeably. So anyone considering a lifecycle fund should be sure whether he or she is getting a fund with a stocks-bond allocation that remains constant (except, perhaps, in response to changing market conditions) or one in which the allocation changes as you age.

Now back to your question. The whole idea of lifecycle and target retirement funds is that you get a fully diversified portfolio in one fund so you don't have to worry about building such a portfolio yourself.

That doesn't mean, of course, that you can't tinker with that diversification by investing outside the fund. You can diversify beyond what most lifecycle and target funds offer by, say, buying a real estate mutual fund or, for that matter, a fund that invests in commodities or precious metals. Doing that might give you some more protection in the event inflation takes off.

Or you could fine tune your overall allocation a bit by adding outside investments. Let's say your target fund has 15 percent of its stock holdings in small-cap stocks and you'd like to boost that percentage to 20 percent or so. Well, you could do that by putting some money in a separate small-cap fund.

But do you need to do this? I don't think most people do. A basic mix of large and small stocks and bonds will work fine in most cases. And, in fact, I think there's a downside to trying to get too fancy.

Adding outside funds to fine tune your asset mix means you've now got to put some real thought into what asset classes to add -- I fear many people will follow the latest fad as opposed to looking to add diversity for the long-term. And you've got to put time and effort into monitoring your holdings to assure that none of your asset classes has become too large or too small a part of your portfolio.

In other words, you're kind of defeating the reason of investing in a lifecycle or target fund to begin with -- to avoid the hassle of picking funds and tracking your allocation.

My take: if you want to do some minor tinkering with your overall allocation by investing in funds outside your lifecycle or target fund and you're up to the extra work, I see no great harm -- and, who knows, you might even improve your portfolio's showing.

But first ask yourself: are you really doing this for sound investing reasons? Or is it because you just have the urge to tinker with your portfolio. If toying around is the real reason, the odds you'll screw things up is probably a lot greater than the chance you'll boost performance.

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Click here for more on target retirement funds.

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Walter Updegrave is a senior editor at MONEY Magazine and is the author of "We're Not in Kansas Anymore: Strategies for Retiring Rich in a Totally Changed World."