Well I can tell you want I have done...
Originally I choose to pass on the Blade 98 because I thought it seemed too light and too hh. But later I ended up playing with the BLX 6.1 95 (and loved it) then I got curious to see if the Blade 98 might have the same characteristics but with more power or a more forgiving frame. So on a lark I bought one!
Because of local availability, when I purchase my first Blade 98, I was forced to buy a grip size one size smaller than usual... this did not turn out to be a problem as I simply added an additional OG and it was fine.
Customization: The first thing I did was open the trap door. There are two tubes and they are filled with light foam. I decided to remove the foam to make room for clear silicone purchased from the local hardware store. Removing the foam was somewhat tedious until I got out the drill then removing the rest was very easy. I removed about 3-4in from each tube. Once the foam was gone, I open the silicone and squirted it in to each tube of the handle of the frame. It was a little messy and I had to use a thin bamboo stick to pack in the silicone. I had a scale next to me the whole time and continued to add silicone until the stock (unstrung) racquet weighed 320g, at which point I carefully cleaned up the buttcap and particularly the trapdoor ridge and sealed the handle. Then I added 2 Turna OGs and an "O" dampener... and strung it up with Black Code 17 originally @ 48 (though next time I dropped the tension to 46lbs... much better).
I ended up with a fantastic racquet... 350g (strung) and 7pts hl... (so I purchased another Blade repeated the process and matched the first spec perfectly).
Absolutely love this racquet... it has completely replaced the BLX 6.1 95 as my main frame. Note: If using a full bed of poly, please string this frame in the mid to upper 40s... the dense string pattern works very well at this tension... more feel, more spin, more power, more forgiveness, larger sweet spot with absolutely no loss of control... I promise!
PS: Don't put any lead in the hoop... you will not need to do this... In fact in stock form it is way too hh already!