Venturing further out of my experience envelope...if I recall the BK117 used 2 weights located just past mid span behind the forward spar to adjust chord wise cg. There had been an ASB issued a long time ago to check this area for separation as corrosion became a problem and the weight shifted or something.
As for using tip weights only for chord wise cg...the only way I have seen this done was with a "product balance" type setup that is found on a Bell 222, 412, 407, etc. This system use 2 weight pockets located near the tip area with one pocket forward of the other. But this was more a dynamic adjustment by moving weight from one pocket to the other and changing the "twist" of the blade to accomplish the cg shift.
This brings up another question...is your initial inquiry about static or dynamic chord wise balance? Using a Bell 206 as the example since you mentioned it was similar...as chopjock brought up if your setup has one blade bolt with an adjustable lead/lag mount then you could change the chord wise balance of the blade in relation to the MR disk rotation center by adjusting the lead/lag position of the blade. For discussion sake...on the Bell 206 the MR assembly is first statically aligned from the blade tips through the MR hub trunnion center. This is needed as you could not run the aircraft at any speed with one blade excessively out of phase to the other - it would be a bucking bronco. But once running you would then fine tune the dynamic chord balance by sweeping (lagging) a blade at the latch bolt or adding chord wise weights to one side of the MR hub. Span wise balance being done with weight at the blade bolt or tip.
I also recall somewhere that the position of the MR pitch horn, whether located on the lead or retreating side of the blade affected chord wise reaction.
Interesting thread as I always have been on the end user side of a product.
Good Luck!
W1