Some of the speakers in the 60's and earlier with inset grills actually had nothing holding them in place except the friction of the frame and cloth against the inside edges of the cabinet. When I got my first pair of real hi-fi speakers (AR 4ax's) I wanted to look at the drivers, and I just (carefully!) put a butter knife into the space between the grill and the cabinet and pried the grill off. No harm done, but I was kind of surprised by how crappy the drivers and baffle looked. No one would want to listen to speakers with the grills removed back then if it meant having to see the hideous looking baffle (glue smears, ugly particle board, not MDF), woofers and (especially) tweeters. The irony is, grill cloth back then was so thick (like burlap!) and acoustically non-transparent that the speakers would have sounded better without the grill cloth between the drivers and our ears. The frequency response was tailored to compensate for the cloth, but still.
For these H-Frames, I won't be removing the grills after they are put in place anyway, so I'm not concerned about the appearance of the Velcro. Grills mounted to the front of the frames, such as yours, are unquestionably much easier to add without having to modify the frames. I just really like the old school look of AR, KLH, Dynaco, Advent, Klipsch (they are STILL made with inset grills), etc., speakers, with the grills flush with the front edges of the cabinet. For those getting Jon's H-Frames, the inner side panels and horizontal brace can be cut back an inch, and grill frames made to fit in the recess, for those who also like the old look. Either way, these are fantastic subs, aren't they?!